OFFSET
1,2
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..10000
MAPLE
lim:=70: S:={}: p:=1: for n from 1 to lim do p:=nextprime(p): S := S union {p-1, 2*p-1, 3*p-1}: od: op(1..lim, S); # Nathaniel Johnston, Sep 28 2011
MATHEMATICA
With[{upto=130}, Select[{#-1, 2#-1, 3#-1}&/@Prime[Range[PrimePi[upto]+1]]//Flatten//Union, #<=upto&]] (* Harvey P. Dale, Apr 22 2016 *) (* or *)
Select[Range@130, Or @@ PrimeQ[(#+1)/{1, 2, 3}] &] (* Giovanni Resta, Apr 30 2019 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Juri-Stepan Gerasimov, Sep 28 2011
EXTENSIONS
Entries checked by R. J. Mathar, Sep 28 2011
STATUS
approved