A107339 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.

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

Offset

1,1

Comments

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.

Links

Table of n, a(n) for n=1..8.

Example

a(1)=5 is a single-digit prime.
a(2)=57=3*19 is a 2-digit 2-almost prime.
a(3)=574=2*7*41 is a 3-digit 3-almost prime.
a(4)=5748=2*2*3*479 is a 4-digit 4-almost prime.
a(5)=57486=2*3*11*13*67 is a 5-digit 5-almost prime.
a(6)=574868=2*2*7*7*7*419 is a 6-digit 6-almost prime.
a(7)=5748688=2*2*2*2*11*89*367 is a 7-digit 7-almost prime.
a(8)=57486888=2*2*2*3*3*3*61*4363 is an 8-digit 8-almost prime.

Crossrefs

Cf. A001222.

Sequence in context: A266278 A103047 A223628 * A139260 A114466 A155642

Adjacent sequences: A107336 A107337 A107338 * A107340 A107341 A107342

Keyword

base,fini,full,nonn

Author

Rick L. Shepherd, May 22 2005

Status

approved