This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A279882 #20 Jul 29 2024 16:55:09 %S A279882 7,15,63,255,4095,16383,262143,1048575,16777215,1073741823,4294967295, %T A279882 274877906943,4398046511103,17592186044415,281474976710655, %U A279882 18014398509481983,1152921504606846975,4611686018427387903,295147905179352825855,4722366482869645213695 %N A279882 a(n) = 2^(prime(n) + 1) - 1. %C A279882 Numbers whose binary representation is 1 repeated (prime(n)+1) times. %C A279882 The only prime term is 7. %F A279882 a(n) = A101304(n) - 2. %F A279882 a(n) = A000225(A008864(n)). - _Felix Fröhlich_, Dec 21 2016 %e A279882 For n=3; a(3) = 2^(prime(3) + 1) - 1 = 2^(5 + 1) - 1 = 2^6 - 1 = 63. %p A279882 A279882:=n->2^(ithprime(n)+1)-1: seq(A279882(n), n=1..30); # _Wesley Ivan Hurt_, Jan 23 2017 %t A279882 f[n_] := 2^(Prime[n]+1)-2; Array[f, 20] (* _Robert G. Wilson v_, Dec 21 2016 *) %t A279882 2^(Prime[Range[20]]+1)-1 (* _Harvey P. Dale_, Jul 29 2024 *) %o A279882 (Magma) [2^(NthPrime(n)+1)-1: n in[1..50]] %o A279882 (PARI) a(n) = 2^(prime(n)+1)-1 \\ _Felix Fröhlich_, Dec 21 2016 %Y A279882 Cf. A101304 (2^(prime(n)+1)+1), A098102 (2^(prime(n)-1)-1), A278741 (2^(prime(n)-1)+1). %K A279882 nonn,easy %O A279882 1,1 %A A279882 _Jaroslav Krizek_, Dec 21 2016