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 A056166 Numbers which are the product of distinct primes raised to prime powers. 18
 1, 4, 8, 9, 25, 27, 32, 36, 49, 72, 100, 108, 121, 125, 128, 169, 196, 200, 216, 225, 243, 288, 289, 343, 361, 392, 441, 484, 500, 529, 675, 676, 800, 841, 864, 900, 961, 968, 972, 1000, 1089, 1125, 1152, 1156, 1225, 1323, 1331, 1352, 1369, 1372, 1444 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 FORMULA Sum_{n>=1} 1/a(n) = Product_{p prime} (1 + Sum_{q prime} 1/p^q) = 1.80728269690724154161... - Amiram Eldar, Oct 11 2020 EXAMPLE 200 is included because 200 = 2^3 * 5^2. MATHEMATICA {1}~Join~Select[Range[1500], AllTrue[FactorInteger[#][[All, -1]], PrimeQ] &] (* Michael De Vlieger, Aug 20 2017 *) PROG (PARI) is(n)=#select(e->!isprime(e), factor(n)[, 2])==0 \\ Charles R Greathouse IV, Sep 18 2015 CROSSREFS Sequence in context: A158340 A350014 A259183 * A093771 A051676 A114129 Adjacent sequences:  A056163 A056164 A056165 * A056167 A056168 A056169 KEYWORD nonn AUTHOR Leroy Quet, Aug 01 2000 EXTENSIONS a(1) added, offset corrected by Charles R Greathouse IV, Sep 18 2015 STATUS approved

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Last modified August 7 21:08 EDT 2022. Contains 355994 sequences. (Running on oeis4.)