A331221 Positive numbers of the form u * v where the decimal representations of u and of v have the same number of digits d for d = 0..9.

1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 252, 256, 289, 324, 361, 400, 403, 441, 484, 529, 574, 576, 625, 676, 729, 736, 765, 784, 841, 900, 961, 976, 1008, 1024, 1089, 1156, 1207, 1225, 1296, 1300, 1369, 1444, 1458, 1462, 1521, 1600

Offset

1,2

Comments

In other words, the terms of this sequence are squares or the products of two decimal anagrams.

Leading zeros are ignored.

If m belongs to the sequence, then 100*m also belongs to the sequence.

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Example

The numbers 12 and 21 are decimal anagrams, so 252 = 12*21 belongs to the sequence.

Prog

(PARI) is(n, base=10) = fordiv (n, d, if (vecsort(digits(d, base))==vecsort(digits(n/d, base)), return (1))); return (0)

Crossrefs

Cf. A331219 (binary analog), A331220 (ternary analog), A331270, A331271.

Sequence in context: A216500 A370785 A069821 * A174452 A174902 A000290

Adjacent sequences: A331218 A331219 A331220 * A331222 A331223 A331224

Keyword

nonn,base

Author

Rémy Sigrist, Jan 12 2020

Status

approved