A107736 -id:A107736 - cp's OEIS frontend

A259078 Heptagonal numbers (A000566) that are other heptagonal numbers divided by 2.

6426, 9875715583923, 15176968126834688342280, 23323916081375479417207129139097, 35844119643974208514403771705730853759974, 55085128439364942192092971212729781713850848998511, 84654649223375294035879228202426981713600292140166013136308

Offset: 1

Colin Barker, Jun 18 2015

			6426 is in the sequence because 6426 is the 51st heptagonal number, and 2*6426 is the 72nd heptagonal number.

Colin Barker, Table of n, a(n) for n = 1..109
Index entries for linear recurrences with constant coefficients, signature (1536796803,-1536796803,1).

Cf. A000566, A075528, A107736, A259079.

LinearRecurrence[{1536796803,-1536796803,1},{6426,9875715583923,15176968126834688342280},20] (* Harvey P. Dale, May 17 2018 *)

Vec(-189*x*(x^2+1372105*x+34)/((x-1)*(x^2-1536796802*x+1)) + O(x^20))

G.f.: -189*x*(x^2+1372105*x+34) / ((x-1)*(x^2-1536796802*x+1)).

A259079 Octagonal numbers (A000567) that are other octagonal numbers divided by 2.

Original entry on oeis.org

280, 373212840, 497012764340408, 661878856450449219400, 881433339438556519000044120, 1173817118196415977287174306335208, 1563188689740940473437573487667885475320, 2081720262768492984525248323578863263574296200

Offset: 1

Colin Barker, Jun 18 2015

Intersection of A000567 and A033579 (even octagonal numbers divided by 2). - Michel Marcus, Jun 20 2015

			280 is in the sequence because 280 is the 10th octagonal number, and 2*280 is the 14th octagonal number.

Colin Barker, Table of n, a(n) for n = 1..163
Index entries for linear recurrences with constant coefficients, signature (1331715,-1331715,1).

Cf. A000567, A075528, A107736, A259078.

LinearRecurrence[{1331715,-1331715,1},{280,373212840,497012764340408},20] (* Harvey P. Dale, Dec 04 2015 *)

Vec(-8*x*(x^2+41580*x+35)/((x-1)*(x^2-1331714*x+1)) + O(x^20))

G.f.: -8*x*(x^2+41580*x+35) / ((x-1)*(x^2-1331714*x+1)).

cp's OEIS Frontend

A259078 Heptagonal numbers (A000566) that are other heptagonal numbers divided by 2.

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