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%I #12 Aug 07 2016 22:21:52
%S 1,3,4,5,6,7,8,10,17,11,13,26,14,15,16,18,41,20,31,21,23,40,24,25,27,
%T 48,28,30,45,33,63,54,34,35,36,37,38,43,68,70,57,115,44,46,85,47,50,
%U 74,73,51,53,87,55,107,56,58,97,60,180,61,64,96,83,65,66,67,71,114,101,100,75,110,136,108,76,77,78,80,124,81
%N a(n) = A249746(A032766(n)).
%H Antti Karttunen, <a href="/A273664/b273664.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A249746(A032766(n)).
%F a(n) = A249824(A254050(n)).
%F a(n) = A249746(A254049(A249745(n))).
%t t = PositionIndex[FactorInteger[#][[1, 1]] & /@ Range[10^6]]; f[n_] := Times @@ Power[If[# == 1, 1, NextPrime@ #] & /@ First@ #, Last@ #] &@ Transpose@ FactorInteger@ n; Flatten@ Map[Position[Lookup[t, FactorInteger[#][[1, 1]]], #] &[f@ f[2 #]] &, Map[Times @@ Power[If[# == 1, 1, NextPrime[#, -1]] & /@ First@#, Last@#] &@ Transpose@ FactorInteger[2 # - 1] &, Floor[#/2] + # & /@ Range@ 80]] (* _Michael De Vlieger_, Aug 07 2016, Version 10 *)
%o (Scheme) (define (A273664 n) (A249746 (A032766 n)))
%Y Cf. A032766, A249745, A249746, A249824, A254049, A254050, A275716.
%Y Cf. also A273669 (natural numbers not in this sequence).
%K nonn
%O 1,2
%A _Antti Karttunen_, Aug 06 2016
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