A186413 a(n) is the number of odd primes p < prime(n)^2 such that prime(n)# + p is prime with prime(n)# primorial of prime(n).

1, 2, 5, 8, 16, 18, 20, 28, 25, 30, 40, 46, 41, 53, 56, 73, 62, 66, 81, 93, 85, 84, 89, 97, 101, 127, 121, 122, 119, 128, 150, 141, 144, 152, 150, 143, 174, 203, 197, 195, 196, 194, 213, 213, 218, 223, 230, 235, 249, 258, 256, 244, 264, 262

Offset

1,2

Comments

a(n) is not so far from prime(n).

Links

Pierre CAMI, Table of n, a(n) for n = 1..176

Example

prime(1)#=2 2+3=5 5>2^2 so a(1)=1
prime(2)#=6 6+5=11,6+7=13 11>3*3 so a(2)=2

Prog

SCRIPT
DIM nn, 1
DIM kk
DIM cc
DIM dd
DIMS tt
DIMS ss
OPENFILEOUT myout, res
LABEL loopn
SET nn, nn+1
SET kk, nn
SET cc, 0
SET dd, 0
LABEL loopk
SET kk, kk+1
IF p(kk)>p(nn)^2 THEN GOTO a
SETS tt, %d, %d, %d\,; nn; p(nn); -p(kk)
PRP p(nn)#-p(kk), tt
IF ISPRIME THEN SET cc, cc+1
IF ISPRP THEN SET cc, cc+1
SETS tt, %d, %d, %d\,; nn; p(nn); p(kk)
PRP p(nn)#+p(kk), tt
IF ISPRIME THEN SET dd, dd+1
IF ISPRP THEN SET dd, dd+1
GOTO loopk
LABEL a
SETS ss, %d, %d, %d\,; nn; cc; dd
WRITE myout, ss
GOTO loopn

Crossrefs

Cf. A185398.

Sequence in context: A285291 A065618 A257548 * A080084 A065093 A361270

Adjacent sequences: A186410 A186411 A186412 * A186414 A186415 A186416

Keyword

nonn

Author

Pierre CAMI, Feb 21 2011

Status

approved