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 A179689 Numbers with prime signature {7,2}, i.e., of form p^7*q^2 with p and q prime. 6
 1152, 3200, 6272, 8748, 15488, 21632, 36992, 46208, 54675, 67712, 107163, 107648, 123008, 175232, 215168, 236672, 264627, 282752, 312500, 359552, 369603, 445568, 476288, 574592, 632043, 645248, 682112, 703125, 789507, 798848, 881792, 1013888 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 OEIS Wiki, Numbers with same prime signature. Will Nicholes, Prime Signatures FORMULA Sum_{n>=1} 1/a(n) = P(2)*P(7) - P(9) = A085548 * A085967 - A085969 = 0.001741..., where P is the prime zeta function.  - Amiram Eldar, Jul 06 2020 MAPLE a:= proc(n) option remember; local k;       for k from 1+ `if` (n=1, 1, a(n-1))         while sort (map (x-> x[2], ifactors(k)[2]), `>`)<>[7, 2]       do od; k     end: seq (a(n), n=1..32);  # Alois P. Heinz, Jan 23 2011 MATHEMATICA f[n_]:=Sort[Last/@FactorInteger[n]]=={2, 7}; Select[Range[10^6], f] PROG (PARI) list(lim)=my(v=List(), t); forprime(p=2, (lim\4)^(1/7), t=p^7; forprime(q=2, sqrt(lim\t), if(p==q, next); listput(v, t*q^2))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 20 2011 CROSSREFS Cf. A006881, A007304, A065036, A085986, A085987, A092759, A178739, A179642, A179643, A179644, A179645, A179646, A179664, A179665, A179666, A179667, A179668, A179669, A179670, A179671, A179672, A179688. Cf. A085548, A085967, A085969. Sequence in context: A114046 A035888 A252438 * A131527 A229590 A269216 Adjacent sequences:  A179686 A179687 A179688 * A179690 A179691 A179692 KEYWORD nonn AUTHOR Vladimir Joseph Stephan Orlovsky, Jul 24 2010 EXTENSIONS Title edited by Daniel Forgues, Jan 22 2011 STATUS approved

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Last modified October 20 16:06 EDT 2020. Contains 337905 sequences. (Running on oeis4.)