A004176 Omit 1's from n.

0, 0, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 2, 3, 4, 5, 6, 7, 8, 9, 20, 2, 22, 23, 24, 25, 26, 27, 28, 29, 30, 3, 32, 33, 34, 35, 36, 37, 38, 39, 40, 4, 42, 43, 44, 45, 46, 47, 48, 49, 50, 5, 52, 53, 54, 55, 56, 57, 58, 59, 60, 6, 62, 63, 64, 65, 66, 67, 68, 69, 70, 7, 72, 73, 74

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• base
• look

Comments

a(210) = 20 is the first term that differs from the variant "strip any leading or trailing digits 1 from n" [where digits 1 "protected" on both sides by digits different from 1 would be preserved]. Up to there, if a(n) is palindromic, then n is not in A359510, but if a(n) is non-palindromic and n is prime, then n is in A359510. - M. F. Hasler, Jan 23 2023

Links

• Rémy Sigrist, Table of n, a(n) for n = 0..10000

Crossrefs

See A004720 for another version.

Cf. A359510 (numbers that can't be written as a palindromic product).

Programs

Mathematica

Table[FromDigits[DeleteCases[IntegerDigits[n],1]],{n,0,3000}] (* Zak Seidov, Dec 08 2010 *)

PARI

a(n) = fromdigits(select(d -> d!=1, digits(n))) \\ Rémy Sigrist, Jul 13 2019

Python

def A004176(n): return int(s) if (s:=str(n).replace('1','')) else 0 # M. F. Hasler, Jan 23 2023