1,1

Table of n, a(n) for n=1..25.

715157 is prime and of the form 7nn7 for n=15.

7100510057 is prime and of the form 7nn7 for n=1005.

Cf. A102897 for sequence of all numbers of form 7nn7. A102500 for the n values corresponding to the primes in this sequence.

Sequence in context: A234757 A232578 A249210 * A301643 A252887 A204403

Adjacent sequences: A102498 A102499 A102500 * A102502 A102503 A102504

easy,nonn,base

Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005

approved