The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A347878 Numbers k for which A003415(sigma(k)) is even. 4
 1, 3, 6, 7, 8, 11, 12, 14, 15, 18, 19, 21, 22, 23, 24, 27, 28, 30, 31, 33, 35, 36, 38, 39, 42, 43, 44, 46, 47, 48, 49, 50, 51, 54, 55, 56, 57, 59, 60, 62, 63, 65, 66, 67, 69, 70, 71, 75, 76, 77, 78, 79, 81, 83, 84, 85, 86, 87, 88, 91, 92, 93, 94, 95, 96, 99, 100, 102, 103, 105, 107, 108, 110, 111, 112, 114, 115 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers k such that A342925(k) == 0 (mod 2). Odd squares present are terms of A347886 squared. Conjecture: A342923 is a subsequence of this sequence. See comments in A347870. LINKS Table of n, a(n) for n=1..77. MATHEMATICA ad[1] = 0; ad[n_] := n * Total@(Last[#]/First[#]& /@ FactorInteger[n]); Select[Range[115], EvenQ[ad[DivisorSigma[1, #]]] &] (* Amiram Eldar, Sep 19 2021 *) PROG (PARI) isA347878(n) = !A347870(n); CROSSREFS Cf. A000203, A003415, A342923, A342925, A347872, A347873, A347877 (complement), A347886. Positions of zeros in A347870. Sequence in context: A374483 A298980 A206586 * A289176 A277851 A047557 Adjacent sequences: A347875 A347876 A347877 * A347879 A347880 A347881 KEYWORD nonn AUTHOR Antti Karttunen, Sep 19 2021 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 8 14:00 EDT 2024. Contains 375021 sequences. (Running on oeis4.)