Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #8 Oct 03 2017 02:12:13
%S 9,49,961,16129,67092481,17179607041,274876858369,4611686014132420609,
%T 5316911983139663487003542222693990401,
%U 383123885216472214589586755549637256619304505646776321
%N Squares of Mersenne primes A000668(n).
%C Sum of last A000043(n) divisors of the n-th even perfect number. In other words; sum of divisors that are not powers of 2 of the n-th even perfect number, or sum of divisors that are multiples of the n-th Mersenne prime A000668(n) of the n-th even perfect number. See A139247 for more information.
%C See the structure of the divisors of perfect numbers in A135652, A135653, A135654 and A135655.
%H G. C. Greubel, <a href="/A133049/b133049.txt">Table of n, a(n) for n = 1..15</a>
%H Omar E. Pol, <a href="http://www.polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>.
%F a(n) = A000668(n)^2
%e a(3)=961 because the 3rd Mersenne prime is 31 and 31^2=961.
%t Select[2^Range[1000] - 1, PrimeQ]^2 (* _G. C. Greubel_, Oct 03 2017 *)
%o (PARI) forprime(p=2, 1000, if(ispseudoprime(2^p-1), print1((2^p-1)^2", "))) \\ _G. C. Greubel_, Oct 03 2017
%Y Cf. A000290, A001248. Mersenne primes: A000668.
%Y Cf. A000043, A000396, A135652, A135653, A135654, A135655, A138247.
%K nonn
%O 1,1
%A _Omar E. Pol_, Oct 30 2007, Apr 23 2008
%E More terms from _Olaf Voß_, Feb 13 2008