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 A243885 Smallest prime p_n which generates n primes of the form (p_n^i - 4) when i runs through the first n odd numbers. 0
 7, 11, 11, 971, 71394923, 959316767, 13342820302307 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The first 4 entries of this sequence are the first entry of the following sequences: A046132 : Larger member p+4 of cousin primes (p, p+4). A243817 : Primes p for which p - 4 and p^3 - 4 are primes. A243818 : Primes p for which p^i - 4 is prime for i = 1, 3 and 5. A243861 : Primes p for which p^i - 4 is prime for i = 1, 3, 5 and 7. LINKS EXAMPLE a(1) = 7 because 7-4 = 3 (prime), a(2) = 11 because 11-4 = 7 (prime) and 11^3 - 4 = 1327 (prime). PROG (Python) import sympy ## isp_list returns an array of true/false for prime number test for a ## list of numbers def isp_list(ls): ....pt=[] ....for a in ls: ........if sympy.ntheory.isprime(a)==True: ............pt.append(True) ....return(pt) co=1 while co > 0: ....al=0 ....n=2 ....while al!=co: ........d=[] ........for i in range(0, co): ............d.append(int(n**((2*i)+1))-4) ........al=isp_list(d).count(True) ........if al==co: ............## Prints prime number and its corresponding sequence d ............print(n, d) ........n=sympy.ntheory.nextprime(n) ....co=co+1 CROSSREFS Cf. A046132, A243817, A243818 and A243861. Sequence in context: A205679 A166980 A184071 * A171017 A195608 A228523 Adjacent sequences: A243882 A243883 A243884 * A243886 A243887 A243888 KEYWORD nonn,hard,more AUTHOR Abhiram R Devesh, Jun 13 2014 EXTENSIONS a(6) from Bert Dobbelaere, Jul 16 2019 a(7) from Giovanni Resta, Jul 18 2019 STATUS approved

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Last modified March 27 12:09 EDT 2023. Contains 361570 sequences. (Running on oeis4.)