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 A259157 Positive triangular numbers (A000217) that are hexagonal numbers (A000384) divided by 2. 3
 3, 3570, 4119885, 4754343828, 5486508657735, 6331426236682470, 7306460390622912753, 8431648959352604634600, 9730115592632515125415755, 11228544962248963102125146778, 12957731156319710787337293966165, 14953210525847983999624135111807740 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Intersection of A000217 and A033991 (even hexagonal numbers divided by 2). - Michel Marcus, Jun 20 2015 LINKS Colin Barker, Table of n, a(n) for n = 1..327 Index entries for linear recurrences with constant coefficients, signature (1155,-1155,1). FORMULA G.f.: -3*x*(35*x+1) / ((x-1)*(x^2-1154*x+1)). EXAMPLE 3 is in the sequence because 3 is the 2nd triangular number, and 2*3 is the 2nd hexagonal number. MATHEMATICA LinearRecurrence[{1155, -1155, 1}, {3, 3570, 4119885}, 20] (* Vincenzo Librandi, Jun 20 2015 *) PROG (PARI) Vec(-3*x*(35*x+1)/((x-1)*(x^2-1154*x+1)) + O(x^20)) CROSSREFS Cf. A000217, A000384, A033991, A259156, A259158-A259167. Sequence in context: A193447 A134909 A286215 * A003831 A200735 A226984 Adjacent sequences: A259154 A259155 A259156 * A259158 A259159 A259160 KEYWORD nonn,easy AUTHOR Colin Barker, Jun 19 2015 STATUS approved

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Last modified July 18 11:13 EDT 2024. Contains 374378 sequences. (Running on oeis4.)