A071590 Numbers k such that reversal(k) < k.

10, 20, 21, 30, 31, 32, 40, 41, 42, 43, 50, 51, 52, 53, 54, 60, 61, 62, 63, 64, 65, 70, 71, 72, 73, 74, 75, 76, 80, 81, 82, 83, 84, 85, 86, 87, 90, 91, 92, 93, 94, 95, 96, 97, 98, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 201, 210, 211, 220, 221, 230, 231

Offset: 1

Author

Benoit Cloitre, Jun 01 2002

Keywords

• nonn
• easy
• base

Links

• David A. Corneth, Table of n, a(n) for n = 1..5400 (first 1000 terms from T. D. Noe)

Crossrefs

Cf. A004086 (digit reversal), A071589 (reversal(k) > k), A002113 (reversal(k) = k).

Cf. A161602 (binary reversal(k) < k).

Programs

Mathematica

Select[Range[300], # > FromDigits[Reverse[IntegerDigits[#]]] &] (* T. D. Noe, Mar 14 2012 *)
Select[Range[300],IntegerReverse[#]<#&] (* Harvey P. Dale, Jan 16 2022 *)

PARI

for(i=2,300,n=(i); s=ceil(log(n)/log(10)); if((sum(i=0,s,10^(s-i-1)*(floor(n/10^i*1.)-10*floor(n/10^(i+1)*1.))))
				

PARI

is(n) = {fromdigits(Vecrev(digits(n)))David A. Corneth, Apr 07 2021

Python

def ok(n): return int(str(n)[::-1]) < n
print([k for k in range(232) if ok(k)]) # Michael S. Branicky, Oct 20 2021

Extensions

Definition corrected by Harvey P. Dale, Jan 16 2022