A071228 a(n) = n*(n-th composite number).

4, 12, 24, 36, 50, 72, 98, 120, 144, 180, 220, 252, 286, 336, 375, 416, 459, 504, 570, 640, 693, 748, 805, 864, 950, 1014, 1080, 1176, 1276, 1350, 1426, 1536, 1617, 1700, 1785, 1872, 1998, 2090, 2184, 2280, 2378, 2520, 2666, 2772, 2880, 2990, 3102

Offset

1,1

Comments

Complement of A171521. - Jaroslav Krizek, Dec 13 2009

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = n * A002808(n). - Jaroslav Krizek, Dec 13 2009

Example

a(1)= 1*4, a(2)= 2*6, a(3)= 3*9, a(4) = 4*10.

Maple

count := 1: for i from 2 to 100 do if isprime(i) then else printf(`%d, `, i*count); count := count+1 fi: od: # James A. Sellers, May 28 2002

Mathematica

Module[{cn=Select[Range[70], CompositeQ]}, Times@@@Thread[{cn, Range[ Length[ cn]]}]] (* Harvey P. Dale, Nov 13 2014 *)

Prog

(PARI) lista(nn) = {my(nc = 0); forcomposite(c=1, nn, nc ++; print1(c*nc, ", "); ); } \\ Michel Marcus, Aug 31 2019

Crossrefs

Cf. A002808, A033286, A171521.

Partial sums of A092930.

Sequence in context: A353795 A317518 A307763 * A304077 A108997 A159795

Adjacent sequences: A071225 A071226 A071227 * A071229 A071230 A071231

Keyword

nonn

Author

Amarnath Murthy, May 17 2002

Extensions

More terms from James A. Sellers, May 28 2002

Edited by N. J. A. Sloane, Jul 02 2008 at the suggestion of R. J. Mathar

Status

approved