A096489 Noncomposite numbers n such that number of decimal digits of n = number of divisors of n.

1, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97

Offset: 1

Author

Labos Elemer, Jun 25 2004

Keywords

• base
• fini
• full
• nonn
• easy

Comments

Only 1 and primes with 2 decimal digits are here, so the sequence is finite: it consists of 1+25-4=22 terms. Part of A008364. Consists of the terms below 100 from A095862.

Crossrefs

Cf. A008364, A095862.

Programs

Mathematica

{u=1, ta=Table[0, {25}]}; Do[s=Apply[Plus, IntegerDigits[n]];s1=Length[IntegerDigits[n]]; If[Equal[s1, DivisorSigma[0, n]], Print[n];ta[[u]]=n;u=u+1], {n, 1, 100}]
Select[Range[100],!CompositeQ[#]&&DivisorSigma[0,#]==IntegerLength[#]&] (* Harvey P. Dale, Jan 29 2024 *)

PARI

print1(1);forprime(p=9,99,print1(", "p)) \\ Charles R Greathouse IV, Apr 27 2011