The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A145919 A000332(n) = a(n)*(3*a(n) - 1)/2. 5
 0, 0, 0, 0, 1, 2, -3, 5, 7, -9, 12, 15, -18, 22, 26, -30, 35, 40, -45, 51, 57, -63, 70, 77, -84, 92, 100, -108, 117, 126, -135, 145, 155, -165, 176, 187, -198, 210, 222, -234, 247, 260, -273, 287, 301, -315, 330, 345, -360, 376, 392, -408, 425, 442, -459, 477 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 COMMENTS As the formula in the description shows, all members of A000332 belong to the generalized pentagonal sequence (A001318). A001318 also lists all nonnegative numbers that belong to A145919. LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 Eric Weisstein's World of Mathematics, Pentagonal Number. Eric Weisstein's World of Mathematics, Pentatope Number. Index entries for linear recurrences with constant coefficients, signature (0,0,3,0,0,-3,0,0,1). FORMULA a(n+3) = A001840(n) when 3 does not divide n, A001840(n)*-1 otherwise. After first two zeros, this sequence consists of all values of A001318(n) and A045943(n)*(-1), n>=0, sorted in order of increasing absolute value. G.f.: (-x^4*(x^4+2*x^3-3*x^2+2*x+1))/((x-1)^3*(1+x^2+x)^3). - Maksym Voznyy (voznyy(AT)mail.ru), Jul 27 2009 EXAMPLE a(6) = -3 and A000332(6) = (-3)(-10)/2 = 15. MATHEMATICA CoefficientList[Series[(-x^4*(x^4 + 2*x^3 - 3*x^2 + 2*x + 1))/((x - 1)^3*(1 + x^2 + x)^3), {x, 0, 50}], x] (* G. C. Greubel, Jun 13 2017 *) PROG (PARI) x='x+O('x^50); concat([0, 0, 0, 0], Vec((-x^4*(x^4 +2*x^3 -3*x^2 +2*x +1))/((x-1)^3*(1+x^2+x)^3))) \\ G. C. Greubel, Jun 13 2017 CROSSREFS Cf. A000326, A145920. Sequence in context: A071423 A211004 A062781 * A058937 A130518 A001840 Adjacent sequences:  A145916 A145917 A145918 * A145920 A145921 A145922 KEYWORD easy,sign AUTHOR Matthew Vandermast, Oct 28 2008 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 20 05:55 EST 2021. Contains 340301 sequences. (Running on oeis4.)