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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 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*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.)