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A346940 Numbers whose square starts with exactly 4 identical digits. 2
2357, 2582, 3334, 4714, 5774, 6667, 8165, 8819, 9428, 10542, 10543, 10544, 10545, 14907, 14908, 14909, 18257, 18258, 18259, 21081, 21082, 21083, 23570, 23571, 25819, 25820, 27888, 27889, 29813, 29814, 31622, 33332, 33333, 33335, 33336, 33337, 33338, 33339, 33340, 33341, 33342 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

Differs from A132391 where only at least 4 identical digits are required; indeed, 10541 is the first term of A132391 that is not in this sequence (see Example section), the next one is 33346.

LINKS

Table of n, a(n) for n=1..41.

EXAMPLE

2357 is a term because 2357^2 = 5555449 starts with four 5's.

10541 is not a term because 10541^2 = 111112681 starts with five 1's.

MATHEMATICA

q[n_] := SameQ @@ (d = IntegerDigits[n^2])[[1 ;; 4]] && d[[5]] != d[[1]]; Select[Range[100, 33350], q] (* Amiram Eldar, Aug 08 2021 *)

PROG

(Python)

def ok(n):

s = str(n*n)

return len(s) > 4 and s[0] == s[1] == s[2] == s[3] != s[4]

print(list(filter(ok, range(33343)))) # Michael S. Branicky, Aug 08 2021

CROSSREFS

Cf. A346941, A346942.

Supersequences: A131573, A132391.

Similar with: A346812 (2 digits), A346891 (3 digits).

Sequence in context: A220626 A136420 A132391 * A134966 A108419 A073037

Adjacent sequences: A346937 A346938 A346939 * A346941 A346942 A346943

KEYWORD

nonn,base

AUTHOR

Bernard Schott, Aug 08 2021

STATUS

approved

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Last modified December 6 09:30 EST 2022. Contains 358608 sequences. (Running on oeis4.)