OFFSET
1,1
COMMENTS
10 times the sum of the divisors of n.
a(n) is also the total number of horizontal rhombuses in the terraces of the n-th level of an irregular stepped pyramid (starting from the top) where the structure of every 36-degree-three-dimensional sector arises after the 36-degree-zig-zag folding of every row of the diagram of the isosceles triangle A237593. The top of the pyramid is a 10-pointed star formed by 10 rhombuses (see Links section).
LINKS
FORMULA
MAPLE
with(numtheory): seq(10*sigma(n), n=1..64);
MATHEMATICA
10*DivisorSigma[1, Range[70]] (* After Harvey P. Dale *)
PROG
(PARI) a(n) = 10 * sigma(n);
(GAP) List([1..70], n->10*Sigma(n)); # After Muniru A Asiru
(Magma) [10*DivisorSigma(1, n): n in [1..70]]; // Vincenzo Librandi, Jul 26 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Omar E. Pol, Jul 13 2019
STATUS
approved