

A178540


a(n) is the smallest ndigit nonpalindromic number m such that sum of the prime factors of m is equal to sum of the prime factors of reversal(m).


0



45, 250, 1131, 12441, 109416, 1002921, 10009577, 100022593, 1000081008, 10000401424, 100000835544, 1000001449713, 10000013519782, 100000013605380, 1000000081310530
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OFFSET

2,1


COMMENTS

If 10 doen't divide n, number of digits of n is l and both numbers n & reversal(n) have the same sum of prime factors then for all positive numbers k, n*(10^(k*l)1)/(10^l1) has the same property (See the mentioned link).


LINKS

Table of n, a(n) for n=2..16.
Carlos Rivera SOPF(N)=SOP(RN)


EXAMPLE

250 = 2*5*5*5, reversal(250) = 2*2*13, sum of the prime factors of both these are equal, namely 17 and since 250 is the smallest 3digit number with this property, so
a(3) = 250.


MATHEMATICA

r[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; sop[n_]:=(b=FactorInteger[n]; l=Length[b]; Sum[b[[k]][[1]]*b[[k]][[2]], {k, l}]); a[n_]:=(For[k=1, 10^(n1)+kŠr[10^(n1)+k]sop[10^(n1)+k]¹sop[r[10^(n1)+k]], k++]; 10^(n1)+k)


CROSSREFS

Cf. A001414, A004086.
Sequence in context: A172118 A127073 A089549 * A351534 A296326 A064561
Adjacent sequences: A178537 A178538 A178539 * A178541 A178542 A178543


KEYWORD

nonn,base


AUTHOR

J. M. Bergot & Farideh Firoozbakht, Dec 24 2010


STATUS

approved



