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.

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

Offset

1,1

Links

Table of n, a(n) for n=1..24.

Chris K. Caldwell and G. L. Honaker, Jr., Prime Curios! 76

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

Cf. A000040, A001743.

Sequence in context: A044327 A044708 A099944 * A044408 A044789 A245005

Adjacent sequences: A329539 A329540 A329541 * A329543 A329544 A329545

Keyword

nonn,base

Author

G. L. Honaker, Jr., Nov 16 2019

Extensions

a(5)-a(10) from Chuck Gaydos

a(11)-a(24) from Giovanni Resta, Nov 18 2019

Status

approved