A247822 Corresponding values of primes p from A247821 and A247838.

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

Offset

1,1

Comments

Conjecture: all terms are Mersenne primes (A000668).

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

Links

Table of n, a(n) for n=1..12.

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)) .

Example

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

Prog

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

Crossrefs

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

Sequence in context: A023344 A297050 A137693 * A247823 A234626 A201846

Adjacent sequences: A247819 A247820 A247821 * A247823 A247824 A247825

Keyword

nonn,more

Author

Jaroslav Krizek, Sep 28 2014

Extensions

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

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

Status

approved