This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A270431 #12 Mar 20 2016 12:56:23 %S A270431 6,7,11,14,15,18,19,21,22,23,24,28,35,38,43,44,45,46,47,51,54,55,56, %T A270431 57,59,60,61,63,66,67,70,71,72,73,76,78,79,83,84,86,87,88,89,91,92,94, %U A270431 95,96,103,107,110,112,115,118,119,122,123,127,129,131,134,135,138,140,142,143,146,150,152,153,157,158,159,162 %N A270431 Numbers n such that A048673(n) and A064216(n) are of opposite parity. %C A270431 See comments in A270434. %H A270431 Antti Karttunen, <a href="/A270431/b270431.txt">Table of n, a(n) for n = 1..17000</a> %F A270431 Other identities. For all n >= 1: %F A270431 A270433(a(n)) = n. %t A270431 f[n_] := (Times @@ Power[If[# == 1, 1, NextPrime@ #] & /@ First@ #, Last@ #] + 1)/2 &@ Transpose@ FactorInteger@ n; g[n_] := Times @@ Power[If[# == 1, 1, NextPrime[#, -1]] & /@ First@ #, Last@ #] &@ Transpose@ FactorInteger[2 n - 1]; Select[Range@ 162, Xor[EvenQ@ f@ #, EvenQ@ g@ #] &] (* _Michael De Vlieger_, Mar 17 2016 *) %o A270431 (Scheme, with _Antti Karttunen_'s IntSeq-library) %o A270431 (define A270431 (NONZERO-POS 1 1 (lambda (n) (- (A000035 (A048673 n)) (A000035 (A064216 n)))))) %Y A270431 Complement: A270430. %Y A270431 Left inverse: A270433. %Y A270431 Cf. A000035, A048673, A064216, A270434. %Y A270431 Cf. also A269861. %K A270431 nonn %O A270431 1,1 %A A270431 _Antti Karttunen_, Mar 17 2016