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A105406
Indices n of primes p(n), p(n+3) such that p(n)+1 and p(n+3)+1 have the same largest prime factor.
0
29, 53, 92, 126, 204, 281, 333, 489, 573, 816, 1169, 1585, 1885, 13906, 24059, 44421, 48142, 53394, 84043, 474045, 489910, 535841, 2135727, 3095936, 3925702, 4858924, 6618689, 8537111, 58246902, 163424560, 188474341, 193910248, 785107460, 847979055, 6040627719, 7900840637
OFFSET
2,1
COMMENTS
No other term <=210000. - Emeric Deutsch, Feb 13 2006
MAPLE
with(numtheory): a:=proc(n) local a, b: a:=factorset(1+ithprime(n)): b:=factorset(1+ithprime(n+3)): if a[nops(a)]=b[nops(b)] then n else fi end: seq(a(n), n=1..10000); # it takes hours - Emeric Deutsch, Feb 13 2006
PROG
(PARI) \prime indices such that gd of prime(x)+ k and prime(x+m) + k are equal divpm1(n, m, k) = { local(x, l1, l2, v1, v2); for(x=2, n, v1 = ifactor(prime(x)+ k); v2 = ifactor(prime(x+m)+k); l1 = length(v1); l2 = length(v2); if(v1[l1] == v2[l2], print1(x", ") ) ) } ifactor(n) = \Vector of the prime factors of n { local(f, j, k, flist); flist=[]; f=Vec(factor(n)); for(j=1, length(f[1]), for(k = 1, f[2][j], flist = concat(flist, f[1][j]) ); ); return(flist) }
CROSSREFS
Sequence in context: A117328 A274227 A230027 * A124284 A054822 A034847
KEYWORD
nonn
AUTHOR
Cino Hilliard, May 01 2005
EXTENSIONS
One more term from Emeric Deutsch, Feb 13 2006
a(21)-a(37) from Donovan Johnson, Apr 03 2008
STATUS
approved