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 A180114 Sigma(A001694(n)), sum of divisors of the powerful number A001694(n). 0
 1, 7, 15, 13, 31, 31, 40, 63, 91, 57, 127, 195, 121, 217, 280, 133, 156, 255, 403, 183, 399, 465, 600, 403, 364, 511, 819, 307, 847, 400, 381, 855, 961, 1240, 741, 931, 1092, 1023, 553, 1651, 781, 1815, 1240, 1281, 1093, 1767, 1953, 871, 2520, 2821, 993, 1995 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE Sigma(2^2)=7, sigma(2^3)=15, sigma(3^2)=13. MAPLE emin := proc(n::posint) local L; if n>1 then L:=ifactors(n)[2]; L:=map(z->z[2], L); min(L) else 0 fi end: L:=[]: for w to 1 do for n from 1 to 144 do sn:=sigma(n); if emin(n)>1 then L:=[op(L), sn]; print(n, ifactor(n), sn, ifactor(sn)) fi; od; od; MATHEMATICA pwfQ[n_] := n == 1 || Min[Last /@ FactorInteger[n]] > 1; DivisorSigma[1, Select[ Range@ 1000, pwfQ]] (* Giovanni Resta, Feb 06 2018 *) CROSSREFS Cf. A001694, A000203, A180090, A180097, A180098. Sequence in context: A290629 A234861 A076401 * A204740 A244536 A237054 Adjacent sequences:  A180111 A180112 A180113 * A180115 A180116 A180117 KEYWORD easy,nonn AUTHOR Walter Kehowski, Aug 10 2010 EXTENSIONS a(1)=1 prepended by and more terms from Giovanni Resta, Feb 06 2018 STATUS approved

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Last modified September 18 10:31 EDT 2020. Contains 337166 sequences. (Running on oeis4.)