A073682 Prime sum of n-th group of successive primes in A073684.

5, 23, 101, 109, 263, 211, 251, 757, 1367, 941, 2053, 1901, 911, 2347, 1861, 1187, 1249, 1303, 2273, 1433, 1493, 1553, 2777, 2927, 44843, 26699, 65713, 4597, 14159, 8069, 18439, 5197, 8819, 9011, 9277, 9419, 33599, 53381, 6761, 6823, 11497, 7013

Offset: 1

Author

Amarnath Murthy, Aug 11 2002

Keywords

• nonn

Comments

Partition the sequence of primes into groups so that the sum of the terms in each group is prime: {2, 3}, {5, 7, 11}, {13, 17, 19, 23, 29}, {31, 37, 41}, {43, 47, 53, 59, 61}, {67, 71, 73}, {79, 83, 89}, {97, 101, 103, 107, 109, 113, 127}, {131, 137, 139, 149, 151, 157, 163, 167, 173}, {179, 181, 191, 193, 197}, ...; A073684(n) is the number of terms in n-th group; A073682(n) is the sum of terms in n-th group; A073683(n) is the first term in n-th group; A077279(n) is the last term in n-th group.

Examples

			a(1)=5 because sum of first two primes 2+3 = 5 is prime;
a(2)=23 because sum of next three primes 5+7+11 = 23 is prime;
a(3)=101 because sum of next five primes 13+17+19+23+29 = 101 is prime.
		

Links

• Zak Seidov, Table of n,a(n) for n = 1..3000
• Zak Seidov, Table of n, A073682(n), A073683(n), A073684(n), A077279(n) for n = 1..3000

Crossrefs

Cf. A073683, A073684, A077279.

Programs

Python

from itertools import count, islice
from sympy import isprime, nextprime
def agen(): # generator of terms
    s, i, p = 0, 1, 2
    while True:
        while not(isprime(s:=s+p)) or i < 2:
            i, p = i+1, nextprime(p)
        yield s
        s, i, p = 0, 1, nextprime(p)
print(list(islice(agen(), 42))) # Michael S. Branicky, May 23 2025

Extensions

More terms from Gabriel Cunningham (gcasey(AT)mit.edu), Apr 10 2003