A046831 Numbers k such that decimal expansion of k^2 contains k as a substring and k does not end in 0.

1, 5, 6, 25, 76, 376, 625, 3792, 9376, 14651, 90625, 109376, 495475, 505025, 890625, 971582, 1713526, 2890625, 4115964, 5133355, 6933808, 7109376, 10050125, 12890625, 48588526, 50050025, 66952741, 87109376, 88027284, 88819024

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• base

Comments

Subsequence of A018834. - Chai Wah Wu, Apr 04 2023

Links

• Giovanni Resta, Table of n, a(n) for n = 1..64

Crossrefs

Cf. A018834, A003226, A008851.

Programs

Haskell

a046831 n = a046831_list !! (n-1)
a046831_list = filter ((> 0) . (`mod` 10)) a018834_list
-- Reinhard Zumkeller, Jul 27 2011

Mathematica

Reap[For[n = 1, n < 10^8, n++, If[Mod[n, 10] != 0, If[StringPosition[ToString[n^2], ToString[n]] != {}, Print[n]; Sow[n]]]]][[2, 1]] (* Jean-François Alcover, Apr 04 2013 *)

Python

from itertools import count, islice
def A046831_gen(startvalue=0): # generator of terms >= startvalue
    return filter(lambda n:n%10 and str(n) in str(n**2), count(max(startvalue,0)))
A046831_list = list(islice(A046831_gen(),20)) # Chai Wah Wu, Apr 04 2023