A107339 - OEIS

%I #2 Mar 30 2012 17:36:43

%S 5,57,574,5748,57486,574868,5748688,57486888

%N Longest sequence of n-digit n-almost primes formed by beginning with a single-digit prime and appending a single decimal digit to each previous term.

%C Each a(n) is an n-digit (n-almost) prime; A001222(a(n))=bigomega(a(n))=n. 5,7,4,8,6,8,8,8 is thus the longest sequence of individual (appended) decimal digits to construct such a sequence.

%e a(1)=5 is a single-digit prime.

%e a(2)=57=3*19 is a 2-digit 2-almost prime.

%e a(3)=574=2*7*41 is a 3-digit 3-almost prime.

%e a(4)=5748=2*2*3*479 is a 4-digit 4-almost prime.

%e a(5)=57486=2*3*11*13*67 is a 5-digit 5-almost prime.

%e a(6)=574868=2*2*7*7*7*419 is a 6-digit 6-almost prime.

%e a(7)=5748688=2*2*2*2*11*89*367 is a 7-digit 7-almost prime.

%e a(8)=57486888=2*2*2*3*3*3*61*4363 is an 8-digit 8-almost prime.

%Y Cf. A001222.

%K base,fini,full,nonn

%O 1,1

%A _Rick L. Shepherd_, May 22 2005