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A259165
Positive heptagonal numbers (A000566) that are pentagonal numbers (A000326) divided by 2.
3
540, 125482435, 29152330292086, 6772727677992549813, 1573453639577432827392256, 365547896447135621647431177175, 84924818396817988252797073116286650, 19729903659220000770419185998874515952681, 4583690677832384200588508141377728222042497188
OFFSET
1,1
COMMENTS
Intersection of A000566 and A193866 (even pentagonal numbers divided by 2). - Michel Marcus, Jun 20 2015
FORMULA
G.f.: -x*(x^2+28015*x+540) / ((x-1)*(x^2-232322*x+1)).
EXAMPLE
540 is in the sequence because 540 is the 15th heptagonal number, and 2*540 is the 27th pentagonal number.
MATHEMATICA
LinearRecurrence[{232323, -232323, 1}, {540, 125482435, 29152330292086}, 20] (* Vincenzo Librandi, Jun 20 2015 *)
PROG
(PARI) Vec(-x*(x^2+28015*x+540)/((x-1)*(x^2-232322*x+1)) + O(x^20))
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Jun 19 2015
STATUS
approved