A278404 Greater number in the least prime-semiprime gap of size n.

3, 9, 29, 101, 346, 247, 6098, 3181, 2878, 2531, 16033, 26615, 114371, 41793, 74506, 39359, 463178, 104677, 248426, 517441, 923743, 506531, 1930846, 584237, 2560202, 4036993, 4570438, 4552391, 7879282, 4417843, 27841082, 5167619, 13683067, 9725141, 47735377, 25045807, 63305698

Offset

1,1

Comments

A prime-semiprime gap of n is defined as the difference between p & q, p being either a prime, A000040, or a semiprime, A001358, and q being the next greater prime or semiprime, see examples.

The corresponding numbers at the start of the prime-semiprime gaps, i.e., a(n)-n, are in A278351.

Links

Bobby Jacobs, Charles R Greathouse IV, Jonathan Vos Post, and Robert G. Wilson v, Table of n, a(n) for n = 1..52

Example

a(1) = 3 since there is a gap of 1 between 2 and 3, both of which are primes.
a(2) = 9 since there is a gap of 2 between 7 and 9, the first is a prime and the second is a semiprime.
a(3) = 29 since there is a gap of 3 between 26, a semiprime, and 29, a prime.
a(6) = 247 because the first prime-semiprime gap of size 6 is between 241 and 247.

Crossrefs

Cf. A037143, A275013, A275014, A275108, A278351.

Sequence in context: A169781 A162998 A275014 * A148941 A079319 A112532

Adjacent sequences: A278401 A278402 A278403 * A278405 A278406 A278407

Keyword

nonn

Author

Bobby Jacobs, Charles R Greathouse IV, Jonathan Vos Post, and Robert G. Wilson v, Nov 20 2016

Status

approved