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URL: https://oeis.org/A260463

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A260463
a(n) is the smallest number not already in the sequence such that a(n)^2 begins with n.
1
1, 5, 6, 2, 23, 8, 27, 9, 3, 10, 34, 11, 37, 12, 39, 4, 42, 43, 14, 45, 46, 15, 48, 49, 16, 51, 52, 17, 54, 55, 56, 18, 58, 59, 188, 19, 61, 62, 63, 20, 203, 65, 66, 21, 213, 68, 69, 22, 7, 71, 72, 229, 73, 74, 235, 75, 24, 241, 77, 78, 247, 25, 251, 80, 81, 257, 26, 83, 263, 84, 267, 85, 86, 273, 87, 276, 88, 28, 89
OFFSET
1,2
COMMENTS
Conjectured to be a permutation of the natural numbers.
Differs from A018851 at n = 25.
FORMULA
a(n) >= sqrt(n) for all n > 0. If a(n) = sqrt(n), then n is a square. Note the converse is false: a(25) = 16.
PROG
(PARI) v=[]; k=1; while(#v<100, d=digits(k^2); D=digits(#v+1); if(#D<=#d, c=1; for(i=1, #D, if(D[i]!=d[i], c=0; break)); if(c&&!vecsearch(vecsort(v), k), v=concat(v, k); k=0)); k++); v
CROSSREFS
Cf. A018851.
Sequence in context: A049253 A072733 A018851 * A226533 A011499 A242813
KEYWORD
nonn,base
AUTHOR
Derek Orr, Jul 26 2015
STATUS
approved