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 A163506 a(n) = n-th odd nonprime * n-th odd number. 1
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified July 18 13:04 EDT 2024. Contains 374378 sequences. (Running on oeis4.)