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 A317325 Multiples of 25 and odd numbers interleaved. 4
 0, 1, 25, 3, 50, 5, 75, 7, 100, 9, 125, 11, 150, 13, 175, 15, 200, 17, 225, 19, 250, 21, 275, 23, 300, 25, 325, 27, 350, 29, 375, 31, 400, 33, 425, 35, 450, 37, 475, 39, 500, 41, 525, 43, 550, 45, 575, 47, 600, 49, 625, 51, 650, 53, 675, 55, 700, 57, 725, 59, 750, 61, 775, 63, 800, 65, 825, 67, 850, 69 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Partial sums give the generalized 29-gonal numbers (A303815). a(n) is also the length of the n-th line segment of the rectangular spiral whose vertices are the generalized 29-gonal numbers. LINKS Colin Barker, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (0,2,0,-1). FORMULA a(2n) = 25*n, a(2n+1) = 2*n + 1. G.f.: x*(1 + 25*x + x^2)/((1 - x)^2*(1 + x)^2). - Vincenzo Librandi, Jul 28 2018 a(n) = 2*a(n-2) - a(n-4) for n>3. - Colin Barker, Jul 29 2018 MAPLE seq(op([25*n, 2*n+1]), n=0..40); # Muniru A Asiru, Jul 28 2018 MATHEMATICA With[{nn=30}, Riffle[25 Range[0, nn], 2 Range[0, nn] + 1]] (* Vincenzo Librandi, Jul 28 2018 *) PROG (Magma) &cat[[25*n, 2*n + 1]: n in [0..30]]; // Vincenzo Librandi, Jul 28 2018 (GAP) Flat(List([0..40], n->[25*n, 2*n+1])); # Muniru A Asiru, Jul 28 2018 (PARI) concat(0, Vec(x*(1 + 25*x + x^2) / ((1 - x)^2*(1 + x)^2) + O(x^60))) \\ Colin Barker, Jul 29 2018 CROSSREFS Cf. A008607 and A005408 interleaved. Column 25 of A195151. Sequences whose partial sums give the generalized k-gonal numbers: A026741 (k=5), A001477 (k=6), zero together with A080512 (k=7), A022998 (k=8), A195140 (k=9), zero together with A165998 (k=10), A195159 (k=11), A195161 (k=12), A195312 k=13), A195817 (k=14). Cf. A303815. Sequence in context: A040612 A040614 A040615 * A040610 A158786 A040611 Adjacent sequences: A317322 A317323 A317324 * A317326 A317327 A317328 KEYWORD nonn,easy,mult AUTHOR Omar E. Pol, Jul 25 2018 STATUS approved

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Last modified December 9 19:36 EST 2022. Contains 358703 sequences. (Running on oeis4.)