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 A357679 #63 Feb 08 2023 07:21:01 %S A357679 21,50,112,220,364,544,760,1104,1566,2046,2664,3280,3784,4512,5618, %T A357679 6726,7686,8844,9940,10950,12324,13944,16020,18430,20200,21424,22684, %U A357679 23980,26668,30988,34584,36990,39754,43210,46206,49298,52812,56112,59858,63366,66970,71434,74884,77224,81192 %N A357679 a(n) = prime(n)*(prime(n-1) + prime(n+1)). %C A357679 21 is the only semiprime term. %C A357679 All terms after 21 are even. %F A357679 a(n) = A000040(n)*A048448(n). %F A357679 a(n) = A006094(n) + A006094(n-1). %t A357679 Array[Prime[# + 1] (Prime[#] + Prime[# + 2]) &, 45] (* _Michael De Vlieger_, Oct 09 2022 *) %o A357679 (PARI) a(n) = prime(n)*(prime(n-1) + prime(n+1)) \\ _Michel Marcus_, Oct 09 2022 %Y A357679 Cf. A000040, A048448, A006094. %Y A357679 Cf. A338529 (first differences). %K A357679 nonn,easy %O A357679 2,1 %A A357679 _Saish S. Kambali_, Oct 09 2022