A176496 a(n) = Sum_{k=1..n} 2^nonprime(k).

2, 18, 82, 338, 850, 1874, 5970, 22354, 55122, 120658, 382802, 1431378, 3528530, 7722834, 24500050, 58054482, 125163346, 259381074, 527816530, 1601558354, 5896525650, 14486460242, 31666329426, 66026067794, 134745544530, 409623451474, 959379265362, 2058890893138

Offset: 1

Author

David Lazar (lazar6(AT)illinois.edu), Apr 19 2010

Keywords

• easy
• nonn

Examples

			a(2) = 2 + 2^A018252(2) = 2 + 2^4 = 18 ; a(3) = 18 + 2^A018252(3) = 18 + 2^6 = 82.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..500

Crossrefs

Cf. A076793, A018252.

Programs

Mathematica

With[{t=Select[Range[50],!PrimeQ[#]&]},Accumulate[2^t]] (* Harvey P. Dale, Feb 14 2023 *)

PARI

a(n) = my(s = 0, k = 1); while(n, if(!isprime(k), s += 2^k; n--); k++); return(s)

Formula

a(1) = 2, a(n) = a(n-1) + 2^A018252(n).