OFFSET
1,3
LINKS
Eric Weisstein's World of Mathematics, Heptagonal Pyramidal Number
MATHEMATICA
imax = 55;
A002413 = LinearRecurrence[{4, -6, 4, -1}, {1, 8, 26, 60}, imax];
Join[{0}, Table[A002413[[i ;; j]] // Total, {i, 1, imax}, {j, i, imax}] // Flatten // Union][[;; imax]] (* Jean-François Alcover, Nov 11 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 21 2018
STATUS
approved