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A154728 Products of three consecutive primes of the form 6n+1 (see A002476). 4
1729, 7657, 21793, 49321, 97051, 175741, 298351, 386389, 559399, 789289, 1089019, 1425829, 1924177, 2665603, 3295273, 3864241, 4631971, 5694079, 6951667, 8103877, 9363547, 10775137, 12307147, 14956219, 18091147, 21243961, 24066037 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Note that a(1)=1729 is the Hardy-Ramanujan number (see taxicab numbers in A001235, A011541).

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

13, 19, 31 are three consecutive primes of the form 6n+1 and 13*19*31 = 7657. - Emeric Deutsch, Jan 21 2009

MAPLE

a := proc (n) if `mod`(ithprime(n), 6) = 1 then ithprime(n) else end if end proc: A := [seq(a(n), n = 1 .. 100)]: seq(A[j]*A[j+1]*A[j+2], j = 1 .. 30); # Emeric Deutsch, Jan 21 2009

MATHEMATICA

Times@@@Partition[Select[Prime[Range[100]], IntegerQ[(#-1)/6]&], 3, 1] (* Harvey P. Dale, Jan 13 2019 *)

CROSSREFS

Cf. A001235, A002476, A011541, A154716, A154717, A154729.

Sequence in context: A130859 A245671 A154716 * A286217 A280428 A194263

Adjacent sequences:  A154725 A154726 A154727 * A154729 A154730 A154731

KEYWORD

easy,nonn

AUTHOR

Omar E. Pol, Jan 18 2009, Jan 21 2009

EXTENSIONS

Extended by Emeric Deutsch, Jan 21 2009

STATUS

approved

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Last modified August 20 05:25 EDT 2019. Contains 326139 sequences. (Running on oeis4.)