A156778 a(n) = n*A007504(n)/2 = n*(sum of first n primes)/2.

0, 1, 5, 15, 34, 70, 123, 203, 308, 450, 645, 880, 1182, 1547, 1967, 2460, 3048, 3740, 4509, 5396, 6390, 7476, 8701, 10051, 11556, 13250, 15093, 17064, 19194, 21460, 23895, 26660, 29616, 32802, 36159, 39830, 43686, 47804, 52193, 56823, 61740

Offset

0,3

Comments

For n>0, the sum of the first n primes, A007504(n), has the opposite parity of n (since both increase by an odd amount, and A007504(n)=2 for n=1).

Links

Table of n, a(n) for n=0..40.

Formula

a(n) = A156780(prime(n))/2, where prime(n) = A000040(n) is the n-th prime.

Prog

(PARI) vector(80, n, n--; sum(i=1, n, prime(i))*n)/2
(PARI) a(n) = n*vecsum(primes(n))/2 \\ Jason Yuen, Feb 03 2025

Crossrefs

Cf. A007504, A156780.

Sequence in context: A084288 A083049 A015627 * A346752 A292955 A295005

Adjacent sequences: A156775 A156776 A156777 * A156779 A156780 A156781

Keyword

nonn

Author

M. F. Hasler, Feb 21 2009

Status

approved