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A145338 a(n) = the smallest prime p where |d(p-1) - d(p+1)| = n. (d(m) = the number of divisors of m.) 1
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 (list; graph; refs; listen; history; text; internal format)
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. [From 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); [From Emeric Deutsch, Oct 11 2008]

CROSSREFS

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

STATUS

approved

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Last modified March 26 14:18 EDT 2019. Contains 321497 sequences. (Running on oeis4.)