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A082232
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Palindromes divisible by their digit sum.
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4
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1, 2, 3, 4, 5, 6, 7, 8, 9, 111, 171, 222, 252, 333, 414, 444, 555, 666, 777, 828, 888, 999, 2112, 2772, 2992, 4224, 4554, 4774, 6336, 6556, 8118, 8338, 8448, 10101, 10701, 10901, 11511, 12321, 13131, 15751, 18981, 19791, 20202, 20502, 20702, 21012, 21112
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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REFERENCES
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P. J. Costello, More Palindromic Niven Numbers, Journal of Recreational Mathematics, vol. 33:1 pp. 18-21 2004-5 Baywood Amityville NY.
W. McDaniel, Palindromic Niven Numbers, Journal of Recreational Mathematics, vol. 24 pp. 164-6 1992 Baywood Amityville NY.
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LINKS
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MAPLE
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dmax:= 6; # to get all terms with at most dmax digits
f1:= proc(n)
local L, Ln, i, r, s, p;
L:= convert(n, base, 10);
Ln:= nops(L);
r:= add(L[i]*10^(Ln-i), i=1..Ln);
s:= convert(L, `+`);
p:= 10^Ln*n+r;
if p mod (2*s) = 0 then p else NULL fi;
end proc:
f2:= proc(n, d)
local L, Ln, i, r, s, p;
L:= convert(n, base, 10);
Ln:= nops(L);
r:= add(L[i]*10^(Ln-i), i=1..Ln);
s:= convert(L, `+`);
p:= 10^(1+Ln)*n+10^Ln*d+r;
if p mod(2*s+d) = 0 then p else NULL fi;
end proc:
A:= {$1..9}:
for d from 2 to dmax do
if d::even then
A:= A union {seq(f1(x), x=10^(d/2-1) .. 10^(d/2)-1)}
else
A:= A union {seq(seq(f2(x, y), x=10^((d-1)/2-1) .. 10^((d-1)/2)-1), y=0..9)}
fi
od:
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MATHEMATICA
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d[n_] := IntegerDigits[n]; Select[Range[20800], Reverse[x = d[#]] == x && Divisible[#, Plus @@ d[#]] &] (* Jayanta Basu, Jul 13 2013 *)
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PROG
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(Python)
A082232 = sorted([int(str(x)+str(x)[::-1]) for x in range(1, 10**5) if not
....int(str(x)+str(x)[::-1]) % sum((int(d) for d in str(x)+str(x)[::-1]))]
....+ [int(str(x)+str(x)[-2::-1]) for x in range(1, 10**5) if not
....int(str(x)+str(x)[-2::-1]) % sum((int(d) for d in str(x)+str(x)[-2::-1]))]) # Chai Wah Wu, Aug 22 2014
(PARI)
rev(n)=r=""; d=digits(n); for(i=1, #d, r=concat(Str(d[i]), r)); eval(r)
for(n=1, 10^5, if(rev(n)==n, if(n%sumdigits(n)==0, print1(n, ", ")))) \\ Derek Orr, Aug 25 2014
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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