A181585 "Early bird" squares: write the square numbers in a string 149162536496481100... . Sequence gives numbers k such that k^2 occurs in the string ahead of its natural place.

7, 8, 21, 25, 46, 97, 129, 161, 196, 221, 245, 258, 277, 296, 350, 436, 460, 592, 661, 694, 789, 804, 875, 877, 1250, 2025, 2221, 3500, 3959, 4020, 5461, 5920, 7925, 9607, 12500, 14772, 19821, 20010, 21825, 22011, 22221, 24012, 25225, 25375, 25388, 26013, 28014

Offset: 1

Author

Zak Seidov, Oct 31 2010

Keywords

• base
• nonn

Comments

Corresponding positions of the k^2's in a string 149162536496481100... are 2, 9, 23, 5, 112, 209, 395, 336, 496, 465, 656, 935, 65, 486, 603, 75, 112, 1115, 2317, 3163, 2329, 1987, 252, 421, 4036, 4279, 7092, ... .

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..145

Crossrefs

Cf. A000290, A116700, A141817.

Programs

Mathematica

s="1";ss={};Do[tsn=ToString[n^2];If[ !StringFreeQ[s,tsn],AppendTo[ss,n];Print[n]];s=s<>tsn,{n,2,99999}];

Python

def aupto(limit):
    s, alst = "", []
    for k in range(1, limit+1):
        ss = str(k*k)
        if ss in s: alst.append(k)
        s += ss
    return alst
print(aupto(28028)) # Michael S. Branicky, Jul 08 2021

Extensions

a(46) and beyond from Michael S. Branicky, Jul 08 2021