A100546 Difference between the smallest semiperimeter (see A063655) and its integer log (A001414) equals 1.

2, 3, 5, 7, 11, 13, 17, 18, 19, 23, 24, 29, 30, 31, 37, 41, 42, 43, 47, 53, 59, 61, 66, 67, 71, 73, 78, 79, 83, 89, 97, 101, 102, 103, 107, 109, 113, 114, 127, 131, 137, 138, 139, 149, 151, 157, 163, 167, 173, 174, 179, 181, 186, 191, 193, 197, 199, 211, 222, 223, 227

Offset

0,1

Comments

Theorem: Except for 24, the sequence is the union of primes and 6*primes.

Links

Table of n, a(n) for n=0..60.

Example

Any prime p, since it has semiperimeter p+1 and its integer log is p.

Mathematica

logint = Function[n, Module[{vn}, vn = Transpose[FactorInteger[n]]; vn[[1]].vn[[2]] ]]; semiperi = Function[n, Min[Divisors[n] + Reverse[Divisors[n]]]]; sq = {}; Do[If[semiperi[k] == logint[k] + 1, AppendTo[sq, k]], {k, 2, 500}]; sq

Crossrefs

Cf. A001414 and A063655.

Sequence in context: A171053 A171055 A117285 * A359373 A117094 A171057

Adjacent sequences: A100543 A100544 A100545 * A100547 A100548 A100549

Keyword

nonn

Author

Carlos Alves, Dec 31 2004

Status

approved