A347747 Positive integers with final digit 6 that are equal to the product of two integers ending with the same digit.

16, 36, 56, 96, 136, 156, 176, 196, 216, 256, 276, 296, 336, 376, 396, 416, 456, 476, 496, 516, 536, 576, 616, 636, 656, 676, 696, 736, 756, 776, 816, 856, 876, 896, 936, 976, 996, 1016, 1036, 1056, 1096, 1116, 1136, 1156, 1176, 1196, 1216, 1236, 1256, 1296, 1316

Offset

1,1

Comments

Union of A324297 and A347253.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

Lim_{n->infinity} a(n)/a(n-1) = 1.

Example

16 = 4*4, 36 = 6*6, 56 = 4*14, 96 = 4*24 = 6*16, 136 = 4*34, 156 = 6*26, ...

Mathematica

a={}; For[n=0, n<=150, n++, For[k=0, k<=n, k++, If[Mod[10*n+6, 10*k+4]==0 && Mod[(10*n+6)/(10*k+4), 10]==4 && 10*n+6>Max[a] || Mod[10*n+6, 10*k+6]==0 && Mod[(10*n+6)/(10*k+6), 10]==6 && 10*n+6>Max[a], AppendTo[a, 10*n+6]]]]; a
tisdQ[n_]:=AnyTrue[{Mod[#, 10], Mod[n/#, 10]}&/@Divisors[n], #[[1]] == #[[2]]&]; Select[10 Range[150]+6, tisdQ] (* Harvey P. Dale, Dec 27 2021 *)

Prog

(Python)
def aupto(lim): return sorted(set(a*b for a in range(4, lim//4+1, 10) for b in range(a, lim//a+1, 10)) | set(a*b for a in range(6, lim//6+1, 10) for b in range(a, lim//a+1, 10)))
print(aupto(1317)) # Michael S. Branicky, Sep 12 2021
(PARI) isok(m) = if ((m % 10) == 6, fordiv(m, d, if ((d % 10) == (m/d % 10), return(1)))); \\ Michel Marcus, Oct 06 2021

Crossrefs

Cf. A017341 (supersequence), A324297, A347253, A347749.

Sequence in context: A223456 A377563 A103843 * A359767 A253260 A144548

Adjacent sequences: A347744 A347745 A347746 * A347748 A347749 A347750

Keyword

nonn,base

Author

Stefano Spezia, Sep 12 2021

Status

approved