A034052 Numbers with multiplicative digital root value 5.

5, 15, 35, 51, 53, 57, 75, 115, 135, 151, 153, 157, 175, 315, 351, 355, 359, 395, 511, 513, 517, 531, 535, 539, 553, 557, 571, 575, 579, 593, 597, 715, 751, 755, 759, 795, 935, 953, 957, 975, 1115, 1135, 1151, 1153, 1157, 1175, 1315, 1351, 1355, 1359, 1395

Offset

1,1

Comments

All digits of a(n) must be odd. - Robert Israel, Oct 19 2015

Links

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

Eric Weisstein's World of Mathematics, Multiplicative Digital Root

Index entries for 10-automatic sequences.

Maple

mdr:= proc(n) option remember;
if n < 10 then return(n) fi;
procname(convert(convert(n, base, 10), `*`))
end proc:
select(mdr=5, [$1..10^5]); # Robert Israel, Oct 19 2015

Mathematica

mrQ[n_]:=NestWhile[Times@@IntegerDigits[#]&, n, #>10&]==5; Select[Range[1395], mrQ[#]&] (* Jayanta Basu, May 30 2013 *)

Prog

(PARI) t(n) = {while(n>9, n=prod(i=1, #n=digits(n), n[i])); n};
for(n=0, 1e4, if(t(n) == 5, print1(n", "))); \\ Altug Alkan, Oct 19 2015

Crossrefs

Cf. A031347, A371561.

Cf. A034048, A002275, A034049, A034050, A034051, this sequence, A034053, A034054, A034055, A034056 (numbers having multiplicative digital roots 0-9).

Sequence in context: A295005 A072186 A051807 * A233348 A061829 A063382

Adjacent sequences: A034049 A034050 A034051 * A034053 A034054 A034055

Keyword

nonn,base,easy

Author

Patrick De Geest, Sep 15 1998

Extensions

Incorrect formula removed by Martin Renner, Oct 19 2015

Status

approved