A354527 -id:A354527 - cp's OEIS frontend

A354525 Numbers k such that A354512(k) = A001221(k).

1, 2, 3, 5, 6, 7, 9, 11, 13, 14, 15, 17, 19, 21, 23, 25, 29, 31, 33, 35, 37, 41, 43, 45, 47, 49, 51, 53, 55, 59, 61, 62, 67, 69, 71, 73, 77, 79, 83, 85, 89, 91, 93, 95, 97, 101, 103, 107, 109, 113, 115, 119, 121, 127, 131, 133, 137, 139, 141, 143, 145, 149, 151, 155, 157

Offset: 1

Jianing Song, Aug 16 2022

Numbers k such that for every prime factor p of k we have gpf(k+p) = p, gpf = A006530.
Numbers k such that for every prime factor p of k, k+p is p-smooth.
If k is an even term, then k+2 is a power of 2, so k is of the form 2*(2^m-1). Those m for which 2*(2^m-1) is a term are listed in A354531.

			15 is a term since the prime factors of 15 are 3,5, and we have gpf(15+3) = 3 and gpf(15+5) = 5.

Jianing Song, Table of n, a(n) for n = 1..8435 (all terms <= 50000)

Cf. A001221, A354512, A006530, A354531, A354532, A354533, A354534.

Indices of 0 in A354527. Complement of A354526.

gpf(n) = vecmax(factor(n)[, 1]);
isA354525(n) = my(f=factor(n)[, 1]); for(i=1, #f, if(gpf(n+f[i])!=f[i], return(0))); 1

A354512 Number of solutions m >= 2 to m - gpf(m) = n, gpf = A006530.

Original entry on oeis.org

0, 1, 1, 0, 1, 2, 1, 0, 1, 1, 1, 0, 1, 2, 2, 0, 1, 0, 1, 1, 2, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 2, 1, 2, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 0, 1, 0, 2, 1, 1, 0, 2, 1, 1, 1, 1, 0, 1, 2, 1, 0, 1, 1, 1, 1, 2, 1, 1, 0, 1, 1, 1, 1, 2, 2, 1, 0, 0, 1, 1, 0, 2, 1, 1, 1, 1, 0, 2

Offset: 1

Jianing Song, Aug 16 2022

Number of primes p such that gpf(n+p) = p (such p must be prime factors of n).
Number of distinct prime factors p of n such that n+p is p-smooth.
Clearly we have a(n) <= omega(n) for all n, omega = A001221. The differences are given by A354527.
Is this sequence unbounded? Note that 4 does not appear until a(1660577).

			a(78) = 2 since the prime factors of 78 are 2,3,13, and we have gpf(78+3) = 3 and gpf(78+13) = 13, so the solutions to m - gpf(m) = 78 are m = 78+3 = 81 or m = 78+13 = 91. Note that gpf(78+2) != 2.
a(12) = 0 since the prime factors of 12 are 2,3, and we have gpf(12+2) != 2 and gpf(12+3) != 3.

Jianing Song, Table of n, a(n) for n = 1..10000

Cf. A006530, A076563, A001221, A354516 (indices of first occurrence of each number), A354527.

Cf. A354514 (0 together with indices of positive terms), A354515 (indices of 0), A354516, A354525 (indices n for which a(n) reaches omega(n)), A354526 (indices n for which a(n) is smaller than omega(n)).

gpf(n) = vecmax(factor(n)[, 1]);
a(n) = my(f=factor(n)[, 1]); sum(i=1, #f, gpf(n+f[i])==f[i])

A354526 Numbers k such that A354512(k) < omega(k); complement of A354525.

Original entry on oeis.org

4, 8, 10, 12, 16, 18, 20, 22, 24, 26, 27, 28, 30, 32, 34, 36, 38, 39, 40, 42, 44, 46, 48, 50, 52, 54, 56, 57, 58, 60, 63, 64, 65, 66, 68, 70, 72, 74, 75, 76, 78, 80, 81, 82, 84, 86, 87, 88, 90, 92, 94, 96, 98, 99, 100, 102, 104, 105, 106, 108, 110, 111, 112, 114, 116, 117

Offset: 1

Jianing Song, Aug 16 2022

Numbers k such that there is a prime factor p of k such that gpf(k+p) != p.

Numbers k such that there is a prime factor p of k such that k+p is not p-smooth.

			57 is a term since the prime factors of 57 are 3,19, and we have gpf(57+3) != 3.

Jianing Song, Table of n, a(n) for n = 1..7946 (all terms <= 10000)

Cf. A001221, A354512, A006530. Indices of positive terms in A354527.

gpf(n) = vecmax(factor(n)[, 1]);
isA354526(n) = my(f=factor(n)[, 1]); for(i=1, #f, if(gpf(n+f[i])!=f[i], return(1))); 0

cp's OEIS Frontend

A354525 Numbers k such that A354512(k) = A001221(k).

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A354512 Number of solutions m >= 2 to m - gpf(m) = n, gpf = A006530.

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A354526 Numbers k such that A354512(k) < omega(k); complement of A354525.

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