A163506 a(n) = n-th odd nonprime * n-th odd number.

1, 27, 75, 147, 225, 297, 429, 525, 663, 855, 1029, 1173, 1375, 1539, 1827, 2015, 2277, 2625, 2849, 3159, 3485, 3741, 4095, 4371, 4655, 5049, 5565, 6105, 6555, 6903, 7259, 7623, 7995, 8375, 8901, 9443, 9855, 10575, 11011, 11455, 11907, 12699, 13175, 13833

Offset

1,2

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

Formula

a(n) = A014076(n)*A005408(n-1). - corrected by R. J. Mathar, Oct 10 2009

Example

a(1) =  1*1 =   1;
a(2) =  9*3 =  27;
a(3) = 15*5 =  75;
a(4) = 21*7 = 147;
a(5) = 25*9 = 225.

Maple

A014076 := proc(n) option remember; local a; if n = 1 then 1; else for a from procname(n-1)+2 by 2 do if not isprime(a) then return a; end if; end do: end if; end proc:
A163506 := proc(n) A014076(n) *(2*n-1); end: seq(A163506(n), n=1..80) ; # R. J. Mathar, Oct 10 2009

Mathematica

A014076 := Select[Range[1, 10000, 2], PrimeOmega[#] != 1 &]; Table[A014076[[n]]*(2*n - 1), {n, 1, 50}] (* G. C. Greubel, Jul 27 2017 *)

Crossrefs

Cf. A005408, A014076.

Sequence in context: A044017 A147651 A325824 * A226357 A255109 A369063

Adjacent sequences: A163503 A163504 A163505 * A163507 A163508 A163509

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jul 29 2009

Extensions

7279 replaced with 7259 by R. J. Mathar, Oct 10 2009

Status

approved