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 A093361 Add/multiply sequence, see example. 15
 1, 3, 7, 11, 27, 33, 69, 77, 141, 151, 251, 263, 407, 421, 617, 633, 889, 907, 1231, 1251, 1651, 1673, 2157, 2181, 2757, 2783, 3459, 3487, 4271, 4301, 5201, 5233, 6257, 6291, 7447, 7483, 8779, 8817, 10261, 10301, 11901, 11943, 13707, 13751, 15687, 15733, 17849 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS It appears that a(2*n+1) = 2*(n + A002623(2*n-1)) + 3. - Carl Najafi, Jan 21 2013 LINKS Harvey P. Dale, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (1,3,-3,-3,3,1,-1). FORMULA a(n) = (1/24)*(4*n^3 + 12*n^2 + 20*n + 33 + (6*n^2 - 9)*(-1)^n). - Ralf Stephan, Dec 02 2004 G.f.: (1 + 2*x + x^2 - 2*x^3 + 7*x^4 - x^6)/((1 + x)^3*(x - 1)^4). - R. J. Mathar, May 20 2013 E.g.f.: ((12 + 15*x + 15*x^2 + 2*x^3)*cosh(x) + (21 + 21*x + 9*x^2 + 2*x^3)*sinh(x))/12. - Stefano Spezia, Apr 18 2023 EXAMPLE a(0) = 1 a(1) = 1+2 a(2) = 1+2*3 a(3) = 1+2*3+4 a(4) = 1+2*3+4*5 a(5) = 1+2*3+4*5+6 a(6) = 1+2*3+4*5+6*7 a(7) = 1+2*3+4*5+6*7+8 a(8) = 1+2*3+4*5+6*7+8*9 MATHEMATICA LinearRecurrence[{1, 3, -3, -3, 3, 1, -1}, {1, 3, 7, 11, 27, 33, 69}, 50] (* Harvey P. Dale, Jun 02 2019 *) CROSSREFS Cf. A002623. Sequence in context: A024459 A001645 A103798 * A227364 A051202 A211674 Adjacent sequences: A093358 A093359 A093360 * A093362 A093363 A093364 KEYWORD nonn,easy AUTHOR Jorge Coveiro, Apr 28 2004 EXTENSIONS More terms from Ralf Stephan, Dec 02 2004 STATUS approved

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Last modified April 15 20:47 EDT 2024. Contains 371696 sequences. (Running on oeis4.)