The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A090009 Begins the earliest length-n chain of primes such that any term in the chain equals the previous term increased by the sum of its digits. 8
 2, 11, 11, 277, 37783, 516493, 286330897, 286330897, 56676324799 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS From the second term on, subsequence of A[2] := A048519. Due to the "exclusive" definition of this sequence, A048523(1) > a(2), but for k >= 3, a(k) = A[k](1) for A[3..9] = A048524 .. A048527, A320878 .. A320880. - M. F. Hasler, Nov 09 2018 LINKS Carlos Rivera, Puzzle 163. P+SOD(P) EXAMPLE 11 begins the earliest chain 11, 13, 17 of three primes such that any term in the chain equals the previous term increased by the sum of its digits, viz., 13 = 11 + 2, 17 = 13 + 4. Hence a(3) = 11. MAPLE with(numtheory); A090009:=proc(q) local a, b, c, d, j, n; d:=0; for n from 1 to q do   a:=0; c:=ithprime(n); j:=c;   while isprime(c) do    a:=a+1; b:=0; while c>0 do b:=b+(c mod 10); c:=trunc(c/10); od;    c:=j+b; j:=c; od;    if a=d+1 then d:=a; lprint(d, ithprime(n)); j:=1;    else if a>d+1 then for j from 1 to a-d do lprint(d+j, ithprime(n)); od; d:=a; fi; fi; od; end: A090009(10000000000); # Paolo P. Lava, Jun 07 2012 PROG (PARI) A090009(n, P=2)=forprime(p=P, , P=p; for(i=2, n, isprime(P=A062028(P))||next(2)); return(p)) P=0; A090009_vec=vector(6, n, P=A090009(n, P)) \\ Takes long for n > 6. - M. F. Hasler, Nov 09 2018 CROSSREFS Cf. A047791, A048519, A062028 (n + digit sum of n). Cf. A048523 .. A048527, A320878 .. A320880. Sequence in context: A292779 A245521 A275617 * A153706 A201187 A068225 Adjacent sequences:  A090006 A090007 A090008 * A090010 A090011 A090012 KEYWORD base,more,nonn AUTHOR Joseph L. Pe, Jan 27 2004 EXTENSIONS a(7)-a(8) from Donovan Johnson, Jan 08 2013 a(9) from Giovanni Resta, Jan 14 2013 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.

Last modified July 24 06:56 EDT 2021. Contains 346273 sequences. (Running on oeis4.)