A346891 Positive numbers whose square starts with exactly 3 identical digits.

149, 298, 334, 472, 667, 745, 882, 1054, 1055, 1056, 1057, 1058, 1490, 1491, 1492, 1493, 1825, 1826, 1827, 2108, 2109, 2356, 2581, 2788, 2789, 2980, 2981, 3161, 3162, 3332, 3333, 3335, 3336, 3337, 3338, 3339, 3340, 3341, 3342, 3343, 3344, 3345, 3346

Offset

1,1

Comments

If m is a term 10*m is another term.

2357 is the first term of A131573 that is not in this sequence (see Example section), the next ones are 2582, 3334, ...

Links

Table of n, a(n) for n=1..43.

Example

149 is a term because 149^2 = 22201 starts with three 2's.
2357 is not a term because 2357^2 = 5555449 starts with four 5's.

Mathematica

Select[Range[32, 3350], (d = IntegerDigits[#^2])[[1]] == d[[2]] == d[[3]] != d[[4]] &] (* Amiram Eldar, Aug 06 2021 *)

Prog

(Python)
def ok(n): s = str(n*n); return len(s) > 3 and s[0] == s[1] == s[2] != s[3]
print(list(filter(ok, range(3347)))) # Michael S. Branicky, Aug 06 2021

Crossrefs

Subsequence of A131573.

Cf. A039685 (similar, with "ends"), A346812 (similar, with 2), A346892.

Sequence in context: A140023 A105843 A131573 * A244661 A146137 A071331

Adjacent sequences: A346888 A346889 A346890 * A346892 A346893 A346894

Keyword

nonn,base

Author

Bernard Schott, Aug 06 2021

Status

approved