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A228187
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Positive numbers which when decremented by the product of their digits produce a square.
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4
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1, 2, 3, 4, 5, 6, 7, 8, 9, 24, 37, 45, 48, 67, 71, 79, 100, 228, 231, 256, 259, 292, 388, 400, 524, 575, 624, 661, 832, 865, 868, 900, 928, 949, 973, 985, 1024, 1089, 1231, 1317, 1344, 1399, 1541, 1549, 1564, 1600, 1612, 1629, 1723, 1759, 2025, 2164, 2209
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OFFSET
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1,2
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LINKS
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EXAMPLE
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388 is a term because 388-(3*8*8) = 196 = 14^2.
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MAPLE
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a:= proc(n) option remember; local d, k, m;
for k from 1+`if`(n=1, 0, a(n-1)) do
d, m:= 1, k;
while m>0 do d:=d*irem(m, 10, 'm') od;
if issqr(k-d) then return k fi
od
end:
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PROG
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(PARI) for(n=0, 10^4, d=digits(n); p=prod(i=1, #d, d[i]); if(issquare(n-p), print(n, ", "))) \\ Derek Orr, Mar 13 2015
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CROSSREFS
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KEYWORD
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base,nonn,easy
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AUTHOR
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STATUS
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approved
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