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 A259210 Positive hexagonal numbers (A000384) that are other hexagonal numbers divided by 3. 2
 15, 567645, 21362755051, 803965923024825, 30256453525753512135, 1138671371184241752666901, 42852758352891300594112643235, 1612720706714039835374593462842225, 60693131033623416811596149786491655551, 2284125291706662961573569665690233502167245 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Colin Barker, Table of n, a(n) for n = 1..219 Index entries for linear recurrences with constant coefficients, signature (37635,-37635,1). FORMULA a(n) = 37635*a(n-1)-37635*a(n-2)+a(n-3). G.f.: -x*(x^2+3120*x+15) / ((x-1)*(x^2-37634*x+1)). EXAMPLE 15 is in the sequence because 15 is the 3rd hexagonal number, and 3*15 is the 5th hexagonal number. PROG (PARI) Vec(-x*(x^2+3120*x+15)/((x-1)*(x^2-37634*x+1)) + O(x^20)) CROSSREFS Cf. A000384, A076139, A121338, A259211. Sequence in context: A096224 A129613 A248734 * A013802 A084878 A013874 Adjacent sequences:  A259207 A259208 A259209 * A259211 A259212 A259213 KEYWORD nonn,easy AUTHOR Colin Barker, Jun 21 2015 STATUS approved

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Last modified February 21 10:49 EST 2019. Contains 320372 sequences. (Running on oeis4.)