login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A291163 a(n) = smallest number k > a(n-1) maximizing the number of primes in all sums a(j)+k, j=1..(n-1), with a(1)=2. 1
2, 3, 4, 9, 10, 27, 34, 69, 70, 429, 430, 1059, 1484, 3537, 8284, 65169, 98464, 2061999, 2210564, 10919799, 11521580, 495385137, 567955604, 1112946057, 4926960394, 365847990027 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..26.

EXAMPLE

a(6)=27 because it is the smallest number producing 3 primes in the sums with all previous terms: a(1)+27 = 2+27 = 29, a(3)+27 = 4+27 = 31, a(5)+27 = 10+27 = 37;

a(7)=34: a(2)+34 = 3+34 = 37, a(4)+34 = 9+34 = 43, a(6)+34 = 27+34 = 61;

a(8)=69 because it is the smallest number producing 4 primes in the sums with all previous terms: a(1)+69 = 2+69 = 71, a(3)+69 = 4+69 = 73, a(5)+69 = 10+69 = 79, a(7)+69 = 34+69 = 103.

PROG

(PARI)

PT(x)={print1(x, ", "); write("b291163.txt", n++, " ", x)};

n=0;

ae=vector(11);

ao=vector(11);

ae[1]=2; PT(ae[1]);

ao[1]=3; PT(ao[1]);

for (m=1, 10, \

   start=(ao[m]+1)/2; \

   for (kh=start, 100*start, k=kh+kh; \

      for(jj=1, m, j=m-jj+1; if(!isprime(k+ao[j]), next(2))); \

      ae[m+1]=k; PT(k); break(1)); \

   start=ae[m+1]/2; \

   for (kh=start, 100*start, k=kh+kh+1; \

      for(jj=1, m+1, j=m-jj+2; if(!isprime(k+ae[j]), next(2))); \

      ao[m+1]=k; PT(k); break(1)))

\\ Hugo Pfoertner, Oct 10 2017

CROSSREFS

Cf. A005115, A103828.

Sequence in context: A098548 A076963 A081871 * A180743 A162662 A068334

Adjacent sequences:  A291160 A291161 A291162 * A291164 A291165 A291166

KEYWORD

nonn,hard,more

AUTHOR

Rainer Rosenthal and Hugo Pfoertner, Oct 07 2017

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 14 20:15 EST 2019. Contains 329130 sequences. (Running on oeis4.)