A357679 a(n) = prime(n)*(prime(n-1) + prime(n+1)).

21, 50, 112, 220, 364, 544, 760, 1104, 1566, 2046, 2664, 3280, 3784, 4512, 5618, 6726, 7686, 8844, 9940, 10950, 12324, 13944, 16020, 18430, 20200, 21424, 22684, 23980, 26668, 30988, 34584, 36990, 39754, 43210, 46206, 49298, 52812, 56112, 59858, 63366, 66970, 71434, 74884, 77224, 81192

Offset: 2

Author

Saish S. Kambali, Oct 09 2022

Keywords

• nonn
• easy

Comments

21 is the only semiprime term.

All terms after 21 are even.

Crossrefs

Cf. A000040, A048448, A006094.

Cf. A338529 (first differences).

Programs

Mathematica

Array[Prime[# + 1] (Prime[#] + Prime[# + 2]) &, 45] (* Michael De Vlieger, Oct 09 2022 *)

PARI

a(n) = prime(n)*(prime(n-1) + prime(n+1)) \\ Michel Marcus, Oct 09 2022

Formula

a(n) = A000040(n)*A048448(n).

a(n) = A006094(n) + A006094(n-1).