

A179679


Smaller of each pair of consecutive primes which sum to a practical number.


0



3, 5, 7, 11, 13, 17, 19, 29, 37, 41, 43, 47, 53, 59, 61, 71, 79, 97, 101, 103, 107, 113, 137, 139, 149, 151, 157, 163, 167, 173, 179, 191, 193, 197, 223, 227, 229, 239, 257, 263, 269, 277, 283, 293, 311, 313, 317, 337, 347, 349, 359, 367, 397, 401, 409, 419, 431
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OFFSET

1,1


COMMENTS

Complement is: 2, 23, 31, 67, 73, 83, 89, 109, 127, 131, 181, 199, 211, ..., .  Robert G. Wilson v, Aug 03 2010


LINKS

Table of n, a(n) for n=1..57.


EXAMPLE

19 is a term because the next consecutive prime is 23, and 19 + 23 = 42, which is a practical number.


MATHEMATICA

PracticalQ[n_] := Module[{f, p, e, prod = 1, ok = True}, If[n < 1  (n > 1 && OddQ[n]), False, If[n == 1, True, f = FactorInteger[n]; {p, e} = Transpose[f]; Do[If[p[[i]] > 1 + DivisorSigma[1, prod], ok = False; Break[]]; prod = prod*p[[i]]^e[[i]], {i, Length[p]}]; ok]]]; First@# & /@ Select[ Partition[ Prime@ Range@ 85, 2, 1], PracticalQ[Plus @@ # ] &] (* Robert G. Wilson v, Aug 03 2010 *)


CROSSREFS

Cf. A000040, A005153.
Sequence in context: A239879 A001097 A117243 * A059362 A212376 A059264
Adjacent sequences: A179676 A179677 A179678 * A179680 A179681 A179682


KEYWORD

nonn


AUTHOR

Jason G. Wurtzel, Jul 24 2010


EXTENSIONS

More terms from Robert G. Wilson v, Aug 03 2010


STATUS

approved



