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A259158 Positive triangular numbers (A000217) that are heptagonal numbers (A000566) divided by 2. 3
171, 355817826, 739874066553765, 1538466018777014327028, 3199027777735470191011289295, 6651936797966044301302839516949686, 13831784604089070782667939513452521937961, 28761287297921206463992005998270360082445758120 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Colin Barker, Table of n, a(n) for n = 1..158

Index entries for linear recurrences with constant coefficients, signature (2079363,-2079363,1).

FORMULA

G.f.: -171*x*(1443*x+1) / ((x-1)*(x^2-2079362*x+1)).

EXAMPLE

171 is in the sequence because 171 is the 18th triangular number, and 2*171 is the 12th heptagonal number.

MATHEMATICA

LinearRecurrence[{2079363, -2079363, 1}, {171, 355817826, 739874066553765}, 20] (* Vincenzo Librandi, Jun 20 2015 *)

PROG

(PARI) Vec(-171*x*(1443*x+1) / ((x-1)*(x^2-2079362*x+1)) + O(x^20))

CROSSREFS

Cf. A000217, A000566, A259156, A259157, A259159-A259167.

Sequence in context: A097844 A076573 A015356 * A252139 A252132 A252131

Adjacent sequences:  A259155 A259156 A259157 * A259159 A259160 A259161

KEYWORD

nonn,easy

AUTHOR

Colin Barker, Jun 19 2015

STATUS

approved

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Last modified August 14 21:07 EDT 2018. Contains 313756 sequences. (Running on oeis4.)