Search: id:A090748 Results 1-1 of 1 results found. %I A090748 %S A090748 1,2,4,6,12,16,18,30,60,88,106,126,520,606,1278,2202,2280,3216,4252, %T A090748 4422,9688,9940,11212,19936,21700,23208,44496,86242,110502,132048, %U A090748 216090,756838,859432,1257786,1398268,2976220,3021376,6972592,13466916 %N A090748 Numbers n such that 2^(n+1) - 1 is prime. %C A090748 Perfect numbers A000396(n) = 2^A133033(n) - 2^a(n), assuming there are no odd perfect numbers. - Omar E. Pol (info(AT)polprimos.com), Feb 24 2008 %C A090748 Number of proper divisors of n-th even perfect number that are multiples of n-th Mersenne prime A000668(n). - Omar E. Pol (info(AT)polprimos.com), Feb 28 2008 %C A090748 Base 2 logarithm of n-th even superperfect number A061652(n). Also base 2 logarithm of n-th superperfect number A019279(n), assuming there are no odd superperfect numbers. - Omar E. Pol (info(AT)polprimos.com), Apr 11 2008 %C A090748 Number of 0's in binary expansion of n-th even perfect number (See A135650). - Omar E. Pol (info(AT)polprimos.com), May 04 2008 %H A090748 O. E. Pol, Determinacion geometrica de los numeros primos y perfectos. %e A090748 a(1) = 1 because 2^2 - 1 = 3 is prime %t A090748 lst={};Do[If[PrimeQ[2^(n+1)-1], AppendTo[lst, n]], {n, 10^5}];lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Aug 21 2008] %Y A090748 a(n) = A000043(n) - 1. A000043 is the main entry for this sequence. %Y A090748 Cf. A000396, A133033, A000668. %Y A090748 Cf. A019279, A061652. %Y A090748 Cf. A135650. %Y A090748 Sequence in context: A141113 A050584 A019280 this_sequence A032465 A089395 A089699 %Y A090748 Adjacent sequences: A090745 A090746 A090747 this_sequence A090749 A090750 A090751 %K A090748 nonn %O A090748 1,2 %A A090748 Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Feb 03 2004 %E A090748 Edited, corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 09 2004 %E A090748 Updated (a(39)) by Omar E. Pol (info(AT)polprimos.com), Jan 23 2009 Search completed in 0.002 seconds