A373370 -id:A373370 - cp's OEIS frontend

A373381 a(n) = gcd(bigomega(n), A056239(n)), where bigomega is number of prime factors with repetition, and A056239 is fully additive with a(p) = primepi(p).

0, 1, 1, 2, 1, 1, 1, 3, 2, 2, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 3, 3, 1, 3, 1, 5, 1, 2, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 2, 1, 6, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 4, 2, 1, 4, 2, 1, 2, 4, 1, 4, 2, 1, 1, 2, 1, 1, 1, 3, 3, 4, 1, 1, 1, 1, 3

Offset: 1

Antti Karttunen, Jun 06 2024

nonn

As A001222 and A056239 are both fully additive sequences, all sequences that give the positions of multiples of some natural number k in this sequence are closed under multiplication, i.e., are multiplicative semigroups; for example A340784.

Antti Karttunen, Table of n, a(n) for n = 1..100000

Cf. A001222, A056239, A340784 (positions of even terms), A353331 (their characteristic function).

Cf. also A354871, A373370.

A056239(n) = if(1==n, 0, my(f=factor(n)); sum(i=1, #f~, f[i, 2] * primepi(f[i, 1])));
A373381(n) = gcd(bigomega(n), A056239(n));

a(n) = gcd(A001222(n), A056239(n)).

A373382 a(n) = gcd(A329697(n), A331410(n)), where A329697, A331410 give the number of iterations needed to reach a power of 2, when using the map n -> n-(n/p), or respectively, n -> n+(n/p), where p is the largest prime factor of n.

Original entry on oeis.org

0, 0, 1, 0, 1, 1, 1, 0, 2, 1, 2, 1, 2, 1, 1, 0, 1, 2, 3, 1, 1, 2, 1, 1, 2, 2, 3, 1, 1, 1, 1, 0, 3, 1, 3, 2, 1, 3, 3, 1, 1, 1, 1, 2, 1, 1, 2, 1, 2, 2, 2, 2, 1, 3, 1, 1, 4, 1, 4, 1, 1, 1, 1, 0, 1, 3, 4, 1, 1, 3, 1, 2, 1, 1, 1, 3, 1, 3, 1, 1, 4, 1, 3, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 4, 2, 1, 2, 3, 2, 4

Offset: 1

Antti Karttunen, Jun 06 2024

nonn

As A329697 and A331410 are both fully additive sequences, all sequences that give the positions of multiples of some natural number k in this sequence are closed under multiplication, i.e., are multiplicative semigroups.

Antti Karttunen, Table of n, a(n) for n = 1..100000

Cf. A329697, A331410, A334861, A335877.

Cf. also A373370.

A329697(n) = { my(f=factor(n)); sum(k=1,#f~,if(2==f[k,1],0,f[k,2]*(1+A329697(f[k,1]-1)))); };
A331410(n) = { my(f=factor(n)); sum(k=1,#f~,if(2==f[k,1],0,f[k,2]*(1+A331410(f[k,1]+1)))); };
A373382(n) = gcd(A329697(n), A331410(n));

a(n) = gcd(A329697(n), A334861(n)) = gcd(A331410(n), A334861(n)).

a(n) = gcd(A329697(n), A335877(n)) = gcd(A331410(n), A335877(n)).

cp's OEIS Frontend

A373381 a(n) = gcd(bigomega(n), A056239(n)), where bigomega is number of prime factors with repetition, and A056239 is fully additive with a(p) = primepi(p).

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