A117102 Least n such that nextprime(p*n) > p*nextprime(n) where p runs through the prime numbers (if p is prime then nextprime(p)=p).

4, 16, 18, 42, 126, 126, 136, 70, 58, 292, 822, 1872, 1446, 1008, 3318, 2026, 2280, 2842, 7726, 17922, 2136, 5022, 20142, 17550, 19540, 68898, 59082, 18792, 90006, 136540, 246888, 392382, 197088, 144060, 819898, 137956, 1555162, 291198, 909772

Offset

0,1

Comments

Is a(n)+1 always prime? Is a(n) always even?

Links

Table of n, a(n) for n=0..38.

Example

For p=2 least n such that f(2*n) > 2*f(n) and n is composite is 4=a(1);
for p=3 least n such that f(3*n) > 3*f(n) and n is composite is 16=a(2).

Prog

(PARI) f(n)=nextprime(n); g(n, a)=for(i=1, a, if(f(n*i)>f(n)*f(i) && !isprime(i), return(i))); forprime (i=1, 150, print1(g(i, 5000000), ", "))

Crossrefs

Sequence in context: A224705 A243298 A139719 * A077476 A282552 A278315

Adjacent sequences: A117099 A117100 A117101 * A117103 A117104 A117105

Keyword

easy,nonn

Author

Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 18 2006

Status

approved