A260463 a(n) is the smallest number not already in the sequence such that a(n)^2 begins with n.

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.

Links

Derek Orr, Table of n, a(n) for n = 1..10000

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

Adjacent sequences: A260460 A260461 A260462 * A260464 A260465 A260466

Keyword

nonn,base

Author

Derek Orr, Jul 26 2015

Status

approved