A272600 Composites k such that p-1 divides k-1 for each prime divisor of k-1.
9, 21, 25, 33, 49, 55, 65, 81, 85, 121, 129, 145, 161, 169, 201, 217, 221, 253, 273, 289, 295, 301, 321, 325, 343, 361, 385, 441, 469, 481, 501, 505, 513, 545, 589, 625, 649, 685, 721, 781, 801, 817, 841, 865, 901, 961, 973, 1001, 1025, 1027, 1081, 1089, 1101, 1135, 1177, 1261, 1281, 1333, 1345, 1369, 1405, 1441, 1501
Offset: 1
Keywords
Links
- Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Crossrefs
Cf. A080062 (composite n such that p-1 divides n-1 for each prime divisor of n).
Programs
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Mathematica
pdkQ[n_]:=Module[{p=FactorInteger[n-1][[;;,1]]-1},AllTrue[(n-1)/p,IntegerQ]]; Select[Range[ 1550],CompositeQ[#]&&pdkQ[#]&] (* Harvey P. Dale, Feb 26 2024 *) -
PARI
forcomposite(n=4, 10^4, my(q=1, f=factor(n-1)[,1]); for(j=1, #f, if((n-1)%(f[j]-1), q=0; break)); if(q, print1(n,", ") ) );
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PARI
is(n)=my(f=factor(n-1)[,1]); for(i=1,#f, if((n-1)%(f[i]-1), return(0))); !isprime(n) && n>1 \\ Charles R Greathouse IV, May 16 2016
Comments