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A348739
Numbers k for which A326042(k) > k.
7
4, 9, 12, 16, 18, 25, 32, 36, 44, 48, 49, 64, 72, 81, 96, 99, 100, 108, 124, 144, 147, 162, 169, 176, 180, 192, 196, 225, 236, 243, 252, 256, 279, 284, 288, 300, 320, 324, 361, 372, 396, 400, 405, 432, 441, 448, 450, 468, 484, 486, 496, 507, 512, 529, 531, 567, 576, 588, 604, 612, 625, 639, 648, 675, 676, 700, 704
OFFSET
1,1
COMMENTS
Terms that occur also in A337386 are: 180, 300, 720, 900, 960, 1008, 1200, 1440, 1620, 1800, 2016, 2400, ...
MATHEMATICA
f1[2, e_] := 1; f1[p_, e_] := NextPrime[p, -1]^e; s1[1] = 1; s1[n_] := Times @@ f1 @@@ FactorInteger[n]; f2[p_, e_] := NextPrime[p]^e; s2[1] = 1; s2[n_] := Times @@ f2 @@@ FactorInteger[n]; Select[Range[700], s1[DivisorSigma[1, s2[#]]] > # &] (* Amiram Eldar, Nov 04 2021 *)
PROG
(PARI)
A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961
A064989(n) = {my(f); f = factor(n); if((n>1 && f[1, 1]==2), f[1, 2] = 0); for (i=1, #f~, f[i, 1] = precprime(f[i, 1]-1)); factorback(f)};
A326042(n) = A064989(sigma(A003961(n)));
isA348739(n) = (A326042(n)>n);
CROSSREFS
Positions of negative terms in A348736.
Cf. A326182 (subsequence after its initial 1), A348738.
Cf. A000203, A003961, A064989, A161942, A191218, A326042, A337386, A348742, A348749 (corresponding odd numbers), A348942.
Sequence in context: A374904 A162645 A351575 * A135572 A337103 A312855
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 02 2021
STATUS
approved