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A067891
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Primes p such that sigma(p+1)=sigma(p-1).
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3
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367, 919, 30593, 95393, 117571, 124759, 147341, 197261, 334541, 344417, 463219, 732257, 755081, 931757, 982759, 1996759, 2401219, 2962697, 3013447, 4722941, 7892827, 13333097, 13358407, 17946259, 19828483, 19855471, 19904981
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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MATHEMATICA
| f[n_]:=Plus@@Divisors[Prime[n]-1]==Plus@@Divisors[Prime[n]+1]; lst={}; Do[If[f[n], AppendTo[lst, Prime[n]]], {n, 9!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Dec 03 2009]
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PROG
| (PARI) for(n=2, 10^8, if(isprime(n) && sigma(n+1)==sigma(n-1), print1(n, ", ")))
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CROSSREFS
| Sequence in context: A060518 A065556 A068357 * A142579 A098823 A173055
Adjacent sequences: A067888 A067889 A067890 * A067892 A067893 A067894
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Mar 02 2002
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EXTENSIONS
| More terms from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Apr 19 2002
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