This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A085061 a(0) = 1; a(n+1) is the largest positive number (of at most two) such that abs(a(n) - a(n+1)) is the smallest prime not occurring earlier as difference of successive terms and a(n) + a(n+1) is composite. 2
 1, 3, 6, 19, 14, 21, 4, 23, 34, 57, 86, 117, 158, 121, 164, 211, 264, 205, 266, 199, 270, 353, 426, 505, 594, 691, 590, 487, 594, 485, 598, 725, 856, 993, 1132, 1281, 1124, 973, 1136, 1303, 1476, 1655, 1474, 1665, 1858, 2055, 2254, 2465, 2242, 2469, 2240, 2473 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Conjecture 1: a(n+5) > a(n). Conjecture 2: There are no numbers which occur more than once. LINKS EXAMPLE a(4) = 14; the smallest prime not occurring earlier as difference of successive terms is 7; there are two numbers x such that abs(14 - x) = 7 and 14 + x is composite, namely x = 7 and x = 21. The larger of these numbers is 21, so a(5) = 21. a(5) = 21; the smallest primes not occurring earlier as difference of successive terms are 11 and 17; there are two numbers x such that abs(21 - x) = 11, namely x = 10 and x = 32, but neither 21 + 10 = 31 nor 21 + 32 = 53 is composite; there are two numbers x such that abs(21 - x) = 17, namely x = 4 and x = 38 and 21 + 38 = 59 is not composite while 21 + 4 = 25 is composite; hence a(6) = 4. PROG (PARI) {in(n, v)=local(j, s, b); j=1; s=matsize(v)[2]; b=1; while(b&&j<=s, if(n==v[j], b=0, j++)); !b} {print1(a=1, ", "); v=[]; for(n=1, 51, p=2; t=1; while(t>0, if(in(p, v), p=nextprime(p+1), if(!isprime(2*a+p), t=0; b=a+p, if(p

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.

Last modified December 7 00:16 EST 2019. Contains 329812 sequences. (Running on oeis4.)