Links:
Khan Academy - online academy with videos
WolframAlpha - calculations online
statistika.bg - statistics basic concepts with videos btu.bg - statistics basic concepts matematika.bg - basic concepts with examples

More:
YouTube channel - 3Blue1Brown
Interesting Jupyter Notebooks

• scientific method introduction;
• solving linear equations and systems (the “slow” way);
• trigonometry. Right triangle, unit circle, functions and graphs, identities;
• high-School geometry, intro to computational geometry.
  => Basic concepts
  => Exercise

• functions (in maths and programming);
• polynomials – idea, representation, operations;
• complex numbers, geometric intuition;
• euler's formula;
• fundamental theorem of algebra.
  => Basic concepts
  => Exercise

• matrices. Operations with matrices;
• vectors and vector spaces. Basis, change of basis;
• inverse matrix;
• determinant, oriented area and volume.
  => Basic concepts
  => Exercise

• limits;
• derivatives – intuition, slope of a function at a point;
• table derivatives;
• rules for calculating derivatives;
• higher-order derivatives;
• riemann sums and integrals. Intuition, oriented area;
• fundamental theorem of calculus;
• extension of calculus to many dimensions – intuition.
  => Basic concepts
  => Exercise

• random variables;
• probability. Definitions: frequency, chance of happening next time;
• events and algebra of events;
• combinatoric rules;
• probability mass function, probability density function, cumulative distribution function;
• central limit theorem.
  => Basic concepts
  => Exercise

• definition. Descriptive and inferential statistics;
• sample and population. Sampling rules;
• moments of distributions;
• covariance and correlation;
• anscombe's quartet;
• simpson's paradox.
  => Basic concepts
  => Exercise

• confidence intervals, confidence level, alpha parameter;
• null and alternate hypothesis
• z-test, t-test, chi-squared;
• ANOVA;
• p-value;
• p-value misconceptions.
  => Basic concepts
  => Exercise

online viewer of Jupyter Notebooks: https://gke.mybinder.org