A166743 a(n) = (2^p - p^2 - 1)/6 where p = prime(n).

1, 13, 321, 1337, 21797, 87321, 1398013, 89478345, 357913781, 22906492017, 366503875645, 1466015503393, 23456248058853, 1501199875789697, 96076792050570001, 384307168202281705, 24595658764946068073

Offset: 3

Author

Tanin (Mirza Sabbir Hossain Beg) (mirzasabbirhossainbeg(AT)yahoo.com), Oct 21 2009

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 3..468

Crossrefs

Cf. A034785, A066872.

Programs

Maple

A166743 := proc(n) p := ithprime(n) ; (2^p-p^2-1)/6 ; end: seq(A166743(n),n=3..20) ; # R. J. Mathar, Oct 25 2009

Mathematica

Table[(2^p-p^2-1)/6,{p,Prime[Range[3,20]]}] (* Harvey P. Dale, May 16 2020 *)

Formula

a(n) = (A034785(n) - A066872(n))/6. - R. J. Mathar, Oct 25 2009

Extensions

Missing exponentiation signs inserted in the definition by R. J. Mathar, Oct 25 2009

Corrected by D. S. McNeil, Aug 20 2010