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A191967 n * (numbers that are not divisible by 3). 6
0, 1, 4, 12, 20, 35, 48, 70, 88, 117, 140, 176, 204, 247, 280, 330, 368, 425, 468, 532, 580, 651, 704, 782, 840, 925, 988, 1080, 1148, 1247, 1320, 1426, 1504, 1617, 1700, 1820, 1908, 2035, 2128, 2262, 2360, 2501, 2604, 2752, 2860, 3015, 3128, 3290, 3408 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

A033579 and A033570 interleaved.

LINKS

Table of n, a(n) for n=0..48.

Eric Weisstein's World of Mathematics, Pentagonal Number

Wikipedia, Pentagonal number

Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1).

FORMULA

a(n) = n * A001651(n).

a(n) = A000326(n) - A142150(n).

a(2*n) = A033579(n) = 4 * A000326(n);

a(2*n+1) = A033570(n) = A000326(2*n+1).

G.f.: x*(1+3*x+6*x^2+2*x^3)/((1+x)^2*(1-x)^3). - Bruno Berselli, Jul 09 2012

a(n) = A182079(3n). - Bruno Berselli, Jul 09 2012

MATHEMATICA

Table[n (6 n - 3 - (-1)^n)/4, {n, 0, 48}] (* Bruno Berselli, Jul 09 2012 *)

PROG

(Haskell)

a191967 n = n * a001651 n

(MAGMA) A001651:=func<n|(6*n-3-(-1)^n)/4>; [n*A001651(n): n in [0..48]]; // Bruno Berselli, Jul 09 2012

(PARI) a(n)=n\2*3*n+if(n%2, n, -n) \\ Charles R Greathouse IV, Oct 07 2015

CROSSREFS

Sequence in context: A038438 A008207 A008101 * A016439 A008108 A301004

Adjacent sequences:  A191964 A191965 A191966 * A191968 A191969 A191970

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, Jul 07 2012

STATUS

approved

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Last modified February 23 16:19 EST 2020. Contains 332176 sequences. (Running on oeis4.)