A074998 Composite numbers which are sandwiched between two numbers having the same unordered canonical form.
4, 6, 12, 18, 30, 34, 42, 51, 55, 56, 60, 72, 86, 92, 94, 102, 108, 138, 142, 144, 150, 160, 180, 184, 186, 192, 198, 202, 204, 214, 216, 218, 220, 228, 236, 240, 243, 248, 249, 266, 270, 282, 300, 302, 304, 312, 320, 322, 328, 340, 341, 348, 392, 394, 412
Offset: 1
Keywords
Examples
34 is sandwiched between 33 and 35 which are of the form p*q where p and q are primes.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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Maple
k := 0: for j from 2 to 5000 do if not isprime(j) then a := ifactors(j-1): b := ifactors(j+1): if sort([seq(a[2][i][2],i= 1..nops(a[2]))])= sort([seq(b[2][i][2],i= 1..nops(b[2]))]) then k := k+1: c[k] := j: fi: fi: od: seq(c[i],i= 1..k);
Extensions
More terms from Sascha Kurz, Aug 22 2002
Offset corrected by Amiram Eldar, Jan 02 2020
Comments