A247822 Corresponding values of primes p from A247821 and A247838.

7, 8191, 8191, 131071, 524287, 524287, 2147483647, 2147483647, 2305843009213693951, 2305843009213693951, 2305843009213693951, 2305843009213693951

Offset: 1

Author

Jaroslav Krizek, Sep 28 2014

Keywords

• nonn
• more

Comments

Conjecture: all terms are Mersenne primes (A000668).

Conjecture: next terms are 2305843009213693951, 2305843009213693951, 2305843009213693951, 2305843009213693951 and 618970019642690137449562111. - Jaroslav Krizek, Mar 25 2015

Examples

			a(2) = 8191 because sigma(sigma(2*A247821(2)-1)) = sigma(sigma(A247838(2))) = 8191.
		

Crossrefs

Cf. A000203, A008438, A247790, A247791, A247820, A247821, A247823, A247954.

Programs

Magma

[SumOfDivisors(SumOfDivisors(n)): n in [A247838(n)]];

Formula

a(n) = sigma(sigma(2*A247821(n)-1)) = A000203(A000203(2*A247821(n)-1)) = A051027(2*A247821(n)-1).

a(n) = sigma(sigma(A247838(n))) = A000203(A000203(A247838(n))) = A051027(A247838(n)).

Extensions

a(7)-a(8) from Jaroslav Krizek, Mar 25 2015

a(9)-a(12) from Giovanni Resta, Feb 14 2020