

A329542


a(n) is the first occurrence of a composite number whose factorization without exponents contains exactly n circular loops (i.e., loops in digits 0, 6, 8, 9) on each side of the equals sign.


0



76, 166, 801, 8067, 38804, 88181, 586668, 3680818, 6899086, 40888802, 168888169, 868862887, 884888909, 4088888618, 6898889086, 40888888618, 108088888891, 864888888892, 1928888888668, 16888888880873, 8848888888909, 40888888888802, 120888888888896, 968888888886830
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OFFSET

1,1


LINKS



EXAMPLE

a(1) = 76 because 76 = 2*2*19, and there is exactly one loop on each side of the equals sign.
a(2) = 166 because 166 = 2*83, and there are exactly two loops on each side of the equals sign, etc. Note that '8' contains two loops.


MATHEMATICA

cntLo[n_] := Plus @@ ({1, 0, 0, 0, 0, 0, 1, 0, 2, 1}[[IntegerDigits[n] + 1]]); cntF[n_] := Plus @@ (cntLo /@ First /@ FactorInteger[n]); a[n_] := Block[{k=1}, While[ cntLo[k] != n  cntF[k] != n  PrimeQ[k], k++]; k]; Array[a, 8] (* Giovanni Resta, Nov 18 2019 *)


CROSSREFS



KEYWORD

nonn,base


AUTHOR



EXTENSIONS

a(5)a(10) from Chuck Gaydos


STATUS

approved



