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A346926
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a(n) is the smallest positive integer whose square starts and ends with exactly n identical digits, and a(n) = 0 when there is no such integer.
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2
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1, 88, 10538, 235700, 0, 57735000, 0, 14907120000, 0, 235702260400000, 0, 7453559925000000, 0, 105409255338950000000, 0, 10540925533894600000000, 0, 14907119849998598000000000, 0, 74535599249992989880000000000, 0, 210818510677891955466600000000000, 0
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OFFSET
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1,2
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COMMENTS
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When a square ends in exactly three identical digits, these digits are necessarily 444 (A039685).
When a square ends with n > 3 identical digits, these last digits are necessarily 0's, and also this is only possible when n is even.
Differs from A174499 where only at least n identical digits are required.
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LINKS
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Table of n, a(n) for n=1..23.
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FORMULA
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a(2*n+1) = 0 for n >= 2.
a(2*n) = A119511(2*n) * 10^n, for n >= 2.
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EXAMPLE
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a(2) = 88 because 88^2 = 7744 starts with two 7's and ends with two 4's, and 88 is the smallest integer whose square starts and ends with exactly 2 identical digits.
a(4) = 235700 because 235700^2 = 55554490000 starts with four 5's and ends with four 0's, and 235700 is the smallest integer whose square starts and ends with exactly 4 identical digits.
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CROSSREFS
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Cf. A039685, A119511, A174499, A346774, A346892.
Sequence in context: A188991 A189201 A052069 * A174499 A048919 A159718
Adjacent sequences: A346923 A346924 A346925 * A346927 A346928 A346929
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KEYWORD
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nonn,base
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AUTHOR
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Bernard Schott, Aug 07 2021
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STATUS
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approved
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