A191000 - OEIS

%I #13 Oct 06 2021 18:18:00

%S 1,0,2,3,13,5,4,7,10,0,19,6,9,21,8,403,79,34,12,39,35,16,129,38,133,

%T 52,30,100,28,18,81,63,24,75,333,66,64,117,99,243,76,60,889,171,88,36,

%U 279,54,484,387,78,48,475,136,1209,208,132,729,112,258,225,84,90,399,1396,162,741,796

%N Greedy inverse of A034690: the smallest number m such that sum of digits of all divisors of m equals n; a(n) = 0 if no such number exists.

%H Michel Marcus, <a href="/A191000/b191000.txt">Table of n, a(n) for n = 1..2000</a>

%e a(5) = 13 because 13 is the smallest number such that sum of digits of all its divisors is equal to 5: 1 + 1 + 3 = 5.

%e a(2) = a(10) = 0 because there is no number such that sum of digits of all its divisors is equal to 2 or 10.

%o (PARI) sdd(n) = sumdiv(n, d, sumdigits(d)); \\ A034690

%o a(n) = if ((n==2) || (n==10), return (0)); my(k=1); while (sdd(k) != n, k++); k; \\ _Michel Marcus_, Oct 06 2021

%Y Cf. A034690.

%K nonn,base

%O 1,3

%A _Jaroslav Krizek_, Jun 15 2011