A270536 a(1) = 0; a(n) is the sum of m < n for which a(m) + n is not prime.

0, 0, 0, 6, 0, 15, 6, 22, 28, 45, 33, 66, 35, 64, 74, 104, 102, 140, 129, 160, 182, 196, 170, 263, 241, 285, 257, 281, 319, 329, 372, 423, 414, 460, 491, 537, 520, 582, 623, 647, 724, 836, 731, 772, 817, 947, 887, 1062, 879, 834, 1076

Offset

1,4

Links

Peter Kagey, Table of n, a(n) for n = 1..1000

Example

a(1) = 0.
a(2) = 0 because 2 + a(1) is prime.
a(3) = 0 because 3 + a(i) is prime for 1 <= i <= 2.
a(4) = 6 because 4 + a(1), 4 + a(2), and 4 + a(3) are nonprime; 1 + 2 + 3 = 6.
a(5) = 0 because 5 + a(i) is prime for 1 <= i <= 4.

Prog

(Java)
public static int[] sequenceD(int n) {
    int[] terms = new int[n];
    terms[0] = 0;
    terms[1] = 0;
    for (int i = 2; i < n; i++) {
        int count = 0;
        for (int j = 1; j < i; j++) {
            if (!prime(terms[j] + i)) {
                count = count + j;
            }
        }
        terms[i] = count;
    }
    return terms;
}
(PARI) lista(nn) = {va = vector(nn); print1(va[1], ", "); for (n=2, nn, va[n] = sum(k=1, n-1, k*(! isprime(n+va[k]))); print1(va[n], ", "); ); } \\ Michel Marcus, Mar 28 2016

Crossrefs

Cf. A270654, which is the sum of m < n for which a(m) + n is prime.

Sequence in context: A175567 A069828 A340951 * A278712 A057401 A308236

Adjacent sequences: A270533 A270534 A270535 * A270537 A270538 A270539

Keyword

easy,nonn

Author

Alec Jones, Mar 28 2016

Status

approved