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 A023515 #29 Jul 06 2024 11:20:17
%S A023515 1,5,14,34,76,142,220,322,436,666,898,1146,1516,1762,2020,2490,3126,
%T A023515 3598,4086,4756,5182,5766,6556,7386,8632,9796,10402,11020,11662,12316,
%U A023515 14350,16636,17946,19042,20710,22498,23706,25590,27220,28890
%N A023515 a(n) = prime(n)*prime(n-1) - 1.
%C A023515 a(1) = 1 assumes the not generally accepted convention prime(0) = 1. - _Klaus Brockhaus_, Dec 23 2010
%H A023515 Muniru A Asiru, <a href="/A023515/b023515.txt">Table of n, a(n) for n = 1..5000</a>
%F A023515 From _Jason Kimberley_, Oct 23 2015: (Start)
%F A023515 a(n) = A006094(n-1) - 1 = A000040(n-1)*A000040(n)-1, for n>1.
%F A023515 a(n) = 2*A102770(n-2), for n>2.
%F A023515 (End)
%p A023515 1,seq(ithprime(n)*ithprime(n-1)-1,n=2..40); # _Muniru A Asiru_, Apr 27 2019
%t A023515 Prepend[Table[Prime@ n Prime[n - 1] - 1, {n, 2, 12}], 1] (* _Michael De Vlieger_, Nov 10 2015 *)
%t A023515 Join[{1},Times@@#-1&/@Partition[Prime[Range[40]],2,1]] (* _Harvey P. Dale_, Jul 06 2024 *)
%o A023515 (Magma) [ NthPrime(n-1)*NthPrime(n)-1: n in [1..50] ]; // _Vincenzo Librandi_, Dec 23 2010; simplified by _Klaus Brockhaus_, Dec 23 2010
%o A023515 (PARI) a(n) = if(n==1, 1, prime(n)*prime(n-1)-1) \\ _Altug Alkan_, Nov 10 2015
%Y A023515 Cf. A120875 (a subsequence).
%K A023515 nonn
%O A023515 1,2
%A A023515 _Clark Kimberling_