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A071219 Numbers m such that the largest prime factor of prime(m) + prime(m+1) equals m. 1
2, 3, 439 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(4), if it exists, is larger than 10^7.

a(4) > 5*10^14, if it exists. - Giovanni Resta, Jul 14 2018

LINKS

Table of n, a(n) for n=1..3.

EXAMPLE

Numbers x such that A006530(A001043(x)) = x.

x = 2 is a term: p(2) + p(3) = 3 + 5 = 8 with largest factor = 2 = x.

x = 3 is a term: p(3) + p(4) = 5 + 7 = 12 with largest factor = 3 = x.

x = 439 is a term: p(439) + p(440) = 3067 + 3079 = 6146 = 2*7*439 = 14x.

MATHEMATICA

DeleteCases[#, 0] &@ MapIndexed[Boole[#1 == First@ #2] First@ #2 &, Map[FactorInteger[Total@ #][[-1, 1]] &, Partition[Prime@ Range[10^6], 2, 1]]] (* Michael De Vlieger, Aug 09 2017 *)

CROSSREFS

Cf. A006530, A001043, A071216-A071218.

Sequence in context: A097654 A156986 A066849 * A109855 A306370 A128874

Adjacent sequences:  A071216 A071217 A071218 * A071220 A071221 A071222

KEYWORD

nonn,bref,more

AUTHOR

Labos Elemer, May 17 2002

EXTENSIONS

Edited by N. J. A. Sloane, Aug 09 2017

STATUS

approved

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Last modified May 14 04:48 EDT 2021. Contains 343872 sequences. (Running on oeis4.)