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A071228
a(n) = n*(n-th composite number).
2
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
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
Partial sums of A092930.
Sequence in context: A353795 A317518 A307763 * A304077 A108997 A159795
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