A145338 a(n) is the smallest prime p where |d(p-1) - d(p+1)| = n. (d(m) = the number of divisors of m.)

7, 2, 11, 197, 23, 37, 47, 401, 59, 1601, 181, 16901, 167, 3137, 179, 577, 419, 1297, 1051, 12101, 359, 739601, 1009, 4357, 1511, 50177, 719, 171610001, 839, 67601, 10657, 9096257, 1439, 240101, 3697, 145540097, 3023, 15877, 2879, 3587237, 2521

Offset

0,1

Comments

a(2n-1) = k^2 + 1, for all positive integers n, where k is some integer; k is even for n >= 2.

Links

Table of n, a(n) for n=0..40.

Example

a(2)=11 because abs(d(10) - d(12)) = 2 while abs(d(p-1) - d(p+1)) < 2 for p=2,3,5 and 7. - Emeric Deutsch, Oct 11 2008

Maple

with(numtheory); a:=proc(n) local j: for j while abs(tau(ithprime(j)-1)-tau(ithprime(j)+1)) <> n do end do: ithprime(j) end proc: seq(a(n), n=0..26); # Emeric Deutsch, Oct 11 2008

Crossrefs

Cf. A145337.

Sequence in context: A147677 A090243 A216150 * A104586 A323995 A040048

Adjacent sequences: A145335 A145336 A145337 * A145339 A145340 A145341

Keyword

nonn

Author

Leroy Quet, Oct 08 2008

Extensions

More terms from R. J. Mathar and Emeric Deutsch, Oct 10 2008

Extended from a(27) onwards by Ray Chandler, Oct 12 2008

Status

approved