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
Keywords
Examples
a(1)= 1*4, a(2)= 2*6, a(3)= 3*9, a(4) = 4*10.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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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 Sellers, May 28 2002
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Mathematica
Module[{cn=Select[Range[70],CompositeQ]},Times@@@Thread[{cn, Range[ Length[ cn]]}]] (* Harvey P. Dale, Nov 13 2014 *) -
PARI
lista(nn) = {my(nc = 0); forcomposite(c=1, nn, nc ++; print1(c*nc, ", "););} \\ Michel Marcus, Aug 31 2019
Formula
a(n) = n * A002808(n). - Jaroslav Krizek, Dec 13 2009
Extensions
More terms from James Sellers, May 28 2002
Edited by N. J. A. Sloane, Jul 02 2008 at the suggestion of R. J. Mathar
Comments