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 A244623 Odd prime powers that are not primes. 3
 1, 9, 25, 27, 49, 81, 121, 125, 169, 243, 289, 343, 361, 529, 625, 729, 841, 961, 1331, 1369, 1681, 1849, 2187, 2197, 2209, 2401, 2809, 3125, 3481, 3721, 4489, 4913, 5041, 5329, 6241, 6561, 6859, 6889, 7921, 9409, 10201, 10609, 11449, 11881, 12167, 12769, 14641, 15625, 16129, 16807, 17161, 18769, 19321, 19683 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Intersection of A061345 and A014076. A014076 set minus A061346. LINKS Jens Kruse Andersen, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A079290(n) at least in the range n=3..94, and perhaps beyond. - R. J. Mathar, Aug 20 2014 Sum_{n>=1} 1/a(n) = 1/2 + Sum_{p prime} 1/(p*(p-1)) = 1/2 + A136141. - Amiram Eldar, Dec 21 2020 MATHEMATICA Join[{1}, Select[Range[1, 20001, 2], PrimePowerQ[#]&&(!PrimeQ[#])&]] (* Harvey P. Dale, Dec 11 2018 *) PROG (Sage) def isA244623(n) :    return(n % 2 == 1 and is_prime_power(n) == 1 and is_prime(n) == 0) [n for n in (1..20000) if isA244623(n)] (PARI) isok(p) = ((p%2) && !isprime(p) && isprimepower(p)) || (p==1); \\ Michel Marcus, Jul 06 2021 CROSSREFS Intersection of A005408 and A025475. Cf. A061345 (odd prime powers), A061346 (odd neither prime nor prime power), A062739 (odd powerful), A075109 (perfect powers), A136141. Sequence in context: A075109 A319165 A319152 * A339127 A117580 A280609 Adjacent sequences:  A244620 A244621 A244622 * A244624 A244625 A244626 KEYWORD nonn AUTHOR Jani Melik, Jul 02 2014 STATUS approved

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Last modified August 15 20:27 EDT 2022. Contains 356148 sequences. (Running on oeis4.)