A281555 Consider any concatenation of the type n = concat(a,b). Sequence lists numbers whose reverses are the sum of the products of some of such couples a and b.

351, 621, 886, 1641, 1901, 2401, 4122, 4322, 5101, 6568, 23913, 30591, 46649, 60291, 90877, 199001, 216322, 223471, 237391, 297498, 394391, 405278, 420552, 425322, 430762, 456478, 470149, 546649, 861226, 910001, 920781, 1740821, 2008541, 2329876, 2348812, 2414722

Offset

1,1

Links

Table of n, a(n) for n=1..36.

Example

3*51 = 153;
6*21 = 126;
8*86 = 688;
1*641 + 16*41 + 164*1 = 1461;
1*901 + 190*1 = 1091.

Maple

with(combinat): with(numtheory): T:=proc(w) local x, y, z; x:=w; y:=0;
for z from 1 to ilog10(x)+1 do y:=10*y+(x mod 10); x:=trunc(x/10); od; y; end:
P:=proc(q) local a, j, k, n; for n from 1 to q do a:={};
for k from 1 to ilog10(n) do a:=a union {(n mod 10^k)*trunc(n/10^k)}; od; a:=choose(a);
for k from 2 to nops(a) do if T(n)=add(a[k][j], j=1..nops(a[k])) then print(n); break; fi; od;
od; end: P(10^9);

Mathematica

Select[Range[10^5], Function[w, MemberQ[Total /@ Rest@ Subsets@ Map[Times @@ Map[FromDigits@ # &, TakeDrop[w, #]] &, Range[Length@ w - 1]], FromDigits@ Reverse@ w]]@ IntegerDigits@ # &] (* Michael De Vlieger, Jan 24 2017, Version 10.3 *)

Crossrefs

Cf. A265737, A267939.

Sequence in context: A025385 A261640 A292990 * A363422 A267939 A355973

Adjacent sequences: A281552 A281553 A281554 * A281556 A281557 A281558

Keyword

nonn,base

Author

Paolo P. Lava, Jan 24 2017

Status

approved