A359278 Antidiagonal sums of A354967.

1, 4, 9, 19, 45, 127, 491, 2597, 18905, 180253, 2176101, 32236029, 571516361, 11885151437, 285237145381, 7794999370341, 239867327549943, 8232788441242931, 312611538663794793, 13040004273788572983

Offset

1,2

Links

Table of n, a(n) for n=1..20.

Formula

a(n) = Sum_{k=1..n} p(k, n-k+1), where p(n,0) = n and p(n,k) = prime(p(n, k-1)) for k >= 1.

Prog

(Python)
from sympy import prime
def nprime(x, y):
    p = x
    for _ in range(y):
        p = prime(p)
    return p
def a(n):
    return sum([nprime(k, n-k) for k in range(1, n+1)])
(PARI) a(n) = sum(k=1, n, my(p=k); for(j=k+1, n, p=prime(p)); p) \\ Andrew Howroyd, Feb 04 2023

Crossrefs

Cf. A000040, A058009, A354967, A345669.

Sequence in context: A034479 A326340 A183304 * A241351 A023377 A187408

Adjacent sequences: A359275 A359276 A359277 * A359279 A359280 A359281

Keyword

nonn,more

Author

Christoph B. Kassir, Feb 03 2023

Extensions

a(9)-a(15) from Andrew Howroyd, Feb 03 2023

a(16)-a(20) from Alois P. Heinz, Feb 03 2023

Status

approved