OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Heptagonal Number
EXAMPLE
Let S(k, m) denote the sum of m heptagonal numbers starting from the k-th. We have
a(1) = S(1, 1);
a(2) = S(13, 2) = S(3, 8);
a(3) = S(133, 98) = S(479, 14) = S(168, 77);
a(4) = S(6773, 1785) = S(810, 6006) = S(7467, 1547) = S(38758, 70).
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Ilya Gutkovskiy, Apr 12 2020
EXTENSIONS
a(4) from Giovanni Resta, Apr 14 2020
STATUS
approved