A337022 a(n) is the number of positive integers <= A070826(n) with at least one odd prime divisor <= prime(n).

0, 1, 7, 57, 675, 9255, 163095, 3190965, 75051075, 2212976535, 69624142665, 2606749381005, 107980344307605, 4687299592683015, 222157161929253705, 11859617311615438365, 704152383312290447535, 43210523173814533171635, 2910538720151462674819545, 207666871186142520765307695

Offset

1,3

Comments

The set of finite differences positive numbers up to A070826(n) with at least one odd prime divisor <= prime(n) is a palindromic set.

Links

Table of n, a(n) for n=1..20.

Formula

a(n+1) = (prime(n+1) - 1)*a(n) + A070826(n). - Jinyuan Wang, Aug 11 2020

a(n) = A002110(n)/2 - A005867(n). - Jamie Morken, Aug 11 2021

Example

a(3) = 7, p = {3, 5}, prime(n)# / 2 = 15, {3, 5, 6, 9, 10, 12, 15} - divisible by 3 or 5.

Prog

(PARI) pm=1; forprime(p=2, 19, pm*=p; my(k=0); for(x=2, pm/2, forprime(q=3, p, if(x%q==0, k++; break))); print1(k, ", ")) \\ Hugo Pfoertner, Aug 11 2020

Crossrefs

Cf. A002110, A070826, A005867.

Sequence in context: A231540 A349116 A337556 * A316442 A289876 A290847

Adjacent sequences: A337019 A337020 A337021 * A337023 A337024 A337025

Keyword

nonn

Author

Zhandos Mambetaliyev, Aug 11 2020

Extensions

a(8)-a(10) from Hugo Pfoertner, Aug 11 2020

More terms from Jinyuan Wang, Aug 11 2020

Status

approved