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A100546 Difference between the smallest semiperimeter (see A063655) and its integer log (A001414) equals 1. 0
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 (list; graph; refs; listen; history; text; internal format)
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 * A117094 A171057 A229786

Adjacent sequences:  A100543 A100544 A100545 * A100547 A100548 A100549

KEYWORD

nonn

AUTHOR

Carlos Alves, Dec 31 2004

STATUS

approved

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Last modified May 31 00:53 EDT 2020. Contains 334747 sequences. (Running on oeis4.)