A394001 a(n) is the greatest y such that A393978(n)^2 - y^2 is an anagram of y^2.

0, 27, 51, 72, 147, 156, 231, 246, 126, 252, 294, 249, 282, 282, 273, 270, 282, 267, 321, 327, 336, 396, 324, 414, 318, 375, 519, 510, 498, 651, 651, 651, 405, 429, 708, 483, 564, 690, 420, 375, 729, 729, 603, 639, 336, 660, 567, 759, 375, 579, 618, 645, 642, 633, 708, 666, 507, 672, 873, 954

Offset

1,2

Comments

All terms are divisible by 3.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

A004186(A393978(n)^2 - a(n)^2) = A004186(a(n)^2).

Example

a(7) = 231 because A393978(7) = 264 and 264^2 = 231^2 + 16335, where 16335 is an anagram of 231^2 = 53361, and 231 is the greatest number that works.

Maple

# given a list of the first N terms of A393978, for some N
g:= proc(x) local s, y, r, L, Lr;
     s:= x^2;
     for y from x-3 by -3 do
       r:= s - y^2;
       if ilog10(r) <> ilog10(y^2) then next fi;
       if sort(convert(r, base, 10)) = sort(convert(y^2, base, 10)) then return y fi
     od
end proc:
g(0):= 0:
map(g, A393978);

Crossrefs

Cf. A004186, A393978, A393998.

Sequence in context: A330279 A102708 A393998 * A154591 A217235 A265683

Adjacent sequences: A393998 A393999 A394000 * A394002 A394003 A394004

Keyword

nonn,base

Author

Robert Israel, Mar 06 2026

Status

approved