A211188 a(n) is the number of distinct prime divisors among the all composites of the form k^2 + 1 between the two primes A002496(n) and A002496(n+1).

0, 2, 2, 4, 5, 2, 5, 6, 2, 13, 5, 17, 3, 12, 11, 15, 9, 6, 21, 11, 6, 7, 3, 7, 7, 18, 7, 10, 6, 14, 11, 7, 6, 29, 2, 6, 22, 10, 10, 6, 16, 12, 6, 5, 11, 15, 6, 24, 12, 13, 19, 21, 15, 45, 3, 17, 6, 11, 24, 15, 9, 9, 6, 28, 3, 7, 7, 26, 10, 55, 14, 21, 24, 8

Offset

1,2

Comments

a(1)=0; for n > 1, a(n) = number of elements of each row in A211175(n).

Links

Michel Lagneau, Table of n, a(n) for n = 1..10000

Maple

with(numtheory) :lst:={}: for n from 2 to 600 do:p:=n^2+1:x:=factorset(p):lst:=lst union x:if type(p, prime)=true then m:=nops(lst minus {p}): printf(`%d, `, m):lst:={}:else fi:od:

Crossrefs

Cf. A002144, A002496, A002522, A134406, A181413, A206400, A211175.

Sequence in context: A073018 A201509 A109295 * A057899 A210200 A119989

Adjacent sequences: A211185 A211186 A211187 * A211189 A211190 A211191

Keyword

nonn

Author

Michel Lagneau, Feb 03 2013

Status

approved