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A278404
Greater number in the least prime-semiprime gap of size n.
2
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
KEYWORD
nonn
STATUS
approved