A353758 Numbers k for which A353749(k) > A353749(sigma(k)), where A353749(k) = phi(k) * A064989(k), and A064989 shifts the prime factorization one step towards lower primes.

3, 5, 7, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 27, 29, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 46, 47, 51, 53, 55, 57, 58, 59, 61, 62, 63, 65, 66, 67, 69, 70, 71, 73, 77, 78, 79, 82, 83, 85, 86, 87, 89, 91, 92, 93, 94, 95, 97, 99, 101, 102, 103, 105, 106, 107, 109, 110, 111, 113, 114, 115, 118, 119, 122, 123, 124

Offset

1,1

Comments

First odd terms in the intersection of this sequence and A348749 are: 529, 605, 1445, 2825, 6125, 6425, 6875, 7025, ...

Links

Table of n, a(n) for n=1..76.

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

Prog

(PARI)
A064989(n) = { my(f=factor(n>>valuation(n, 2))); for(i=1, #f~, f[i, 1] = precprime(f[i, 1]-1)); factorback(f); };
A353749(n) = (eulerphi(n)*A064989(n));
A353760(n) = { my(s=sigma(n)); (A353749(s)<A353749(n)); };
isA353758(n) = A353760(n);

Crossrefs

Positions of negative terms in A353757.

Cf. A353749, A353750, A353759 (complement), A353760 (characteristic function), A353765 (conjectured to be a subsequence).

Cf. also A348749, A353684, A353685.

Sequence in context: A361445 A161554 A328944 * A245644 A371168 A370811

Adjacent sequences: A353755 A353756 A353757 * A353759 A353760 A353761

Keyword

nonn

Author

Antti Karttunen, May 10 2022

Status

approved