A378515 Smallest n-digit number whose digits can be divided into an even number of substrings s_i (where i <= n) such that the sum of s_j^s_k (where j <= n and k <= n), with each substring used only once, equals the number k itself, or -1 if no such number exists.

25, -1, 4096, 15626, 117650, 1015626, 10077696, 100015628

Offset

2,1

Comments

Leading zeros in the substrings are not allowed.

Uses the convention that 0^0 = 1.

Links

Table of n, a(n) for n=2..9.

Example

25 = 5^2;
4096 = 4^6 + 0^9;
15626 = 1^26 + 5^6;
117650 = 1^1 + 7^6 + 0^5;
1015626 = 10^6 + 1^2 + 5^6;
10077696 = 0^1 + 0^776 + 6^9;
100015628 = 10^8 + 0^0 + 2^1 + 5^6.

Crossrefs

Cf. A377012, A004248.

Sequence in context: A040649 A104707 A353700 * A040618 A040619 A040617

Adjacent sequences: A378512 A378513 A378514 * A378516 A378517 A378518

Keyword

sign,base,more

Author

Jean-Marc Rebert, Nov 29 2024

Extensions

a(9) from Jinyuan Wang, Dec 01 2024

Status

approved