1,1

1. a(5) > 2*10^9 2. (C. Pomerance) The prime k-tuple conjecture implies a(n) exists for all n

105=3*5*7 and 2*3*5*7+1, 3*5*7+2, 2*5*7+3, 2*3*7+5, 2*3*5+7, 2*3+5*7, 2*5+3*7, 2*7+3*5 are all primes and 105 is the smallest such integer which is the product of 3 odd primes, so a(3)=105

Sequence in context: A048599 A129731 A088109 this_sequence A107878 A120016 A074519

Adjacent sequences: A128273 A128274 A128275 this_sequence A128277 A128278 A128279

hard,more,nonn

Kok Seng Chua (chuakokseng(AT)hotmail.com), Feb 23 2007