

A129733


List of primitive prime divisors of the numbers (3^n1)/2 (A003462) in their order of occurrence.


6



2, 13, 5, 11, 7, 1093, 41, 757, 61, 23, 3851, 73, 797161, 547, 4561, 17, 193, 1871, 34511, 19, 37, 1597, 363889, 1181, 368089, 67, 661, 47, 1001523179, 6481, 8951, 391151, 398581, 109, 433, 8209, 29, 16493, 59, 28537, 20381027, 31, 271, 683
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OFFSET

1,1


COMMENTS

Read A003462 termbyterm, factorize each term, write down any primes not seen before.
Except for n=2, there is at least one primitive prime divisor for every n.  T. D. Noe, Mar 01 2010


LINKS



MAPLE

# produce sequence
s1:=(a, b, M)>[seq( (a^nb^n)/(ab), n=0..M)];
# find primes and their indices
s2:=proc(s) local t1, t2, i; t1:=[]; t2:=[];
for i from 1 to nops(s) do if isprime(s[i]) then
t1:=[op(t1), s[i]];
t2:=[op(t2), i1]; fi; od; RETURN(t1, t2); end;
# get primitive prime divisors in order
s3:=proc(s) local t2, t3, i, j, k, np; t2:=[]; np:=0;
for i from 1 to nops(s) do t3:=ifactors(s[i])[2];
for j from 1 to nops(t3) do p := t3[j][1]; new:=1;
for k from 1 to np do if p = t2[k] then new:= 1; break; fi; od;
if new = 1 then np:=np+1; t2:=[op(t2), p]; fi; od; od;
RETURN(t2); end;


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



