

A067589


Numbers k such that A067588(k) is an odd number.


5



1, 5, 7, 15, 35, 51, 57, 77, 117, 145, 155, 187, 247, 287, 301, 345, 425, 477, 495, 551, 651, 715, 737, 805, 925, 1001, 1027, 1107, 1247, 1335, 1365, 1457, 1617, 1717, 1751, 1855, 2035, 2147, 2185, 2301, 2501, 2625, 2667, 2795, 3015, 3151, 3197, 3337
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OFFSET

1,2


COMMENTS

The terms are exactly the odd pentagonal numbers; that is, they are all the odd numbers of the form k*(3*k1)/2 where k is an integer.  James A. Sellers, Jun 09 2007
Apparently groups of two odd pentagonal numbers (A000326, A014632) followed by two odd 2nd pentagonal numbers (A005449), which leads to the conjectured generating function x*(x^2+4*x+1)*(x^42*x^3+4*x^22*x+1)/((x^2+1)^2*(1x)^3).  R. J. Mathar, Jul 26 2009
Odd generalized pentagonal numbers.  Omar E. Pol, Aug 19 2011


LINKS



FORMULA



MATHEMATICA

With[{nn=50}, Sort[Select[Table[(n(3n1))/2, {n, nn, nn}], OddQ]]] (* Harvey P. Dale, Feb 16 2014 *)


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



EXTENSIONS



STATUS

approved



