OFFSET
1,1
COMMENTS
The number ABCDEF (A through F are digits) is divisible by 37 if the number XYZ (where X=A+D, Y=B+E, Z=C+F) is divisible by 37. If the digit sum of XYZ is S, then the digit sum of ABCDEF is S+9k for some k. A quick check of all multiples of 37 with three or fewer digits shows that none have a digit sum of 8. Thus no multiple of 37 has a digit sum of 8 and a(37) is undefined as is a(37p) for all p. - Christopher Lund (clund(AT)san.rr.com), Apr 16 2002
a(n) = 0 if n is a multiple of 3, 37, 271 or 4649. - Robert Israel, Feb 14 2024
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = n*A088397(n).
MAPLE
unfinished:= true: V:= Vector(1000): V0:= select(t -> igcd(t, 3*37*271*4649) = 1, {$1..1000}):
for i1 from 0 while unfinished do
for i2 from 0 to i1 while unfinished do
for i3 from 0 to i2 while unfinished do
for i4 from 0 to i3 while unfinished do
for i5 from 0 to i4 while unfinished do
for i6 from 0 to i5 while unfinished do
for i7 from 0 to i6 while unfinished do
for i8 from 0 to i7 while unfinished do
v:= 10^i1 + 10^i2 + 10^i3 + 10^i4 + 10^i5 + 10^i6 + 10^i7 + 10^i8;
dv:= numtheory:-divisors(v);
for s in V0 intersect dv do
V[s]:= v;
od;
V0:= V0 minus dv;
unfinished:= evalb(V0 <> {});
od od od od od od od od:
convert(V, list); # Robert Israel, Feb 14 2024
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Apr 01 2002
EXTENSIONS
More terms from Christopher Lund (clund(AT)san.rr.com), Apr 16 2002
STATUS
approved