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A156604 a(1)=2; for n > 0, a(n+1) is the smallest prime of A046704 larger than a(n) such that the sequence of digit sums of a(n) is nondecreasing. 4
2, 3, 5, 7, 29, 47, 67, 89, 179, 197, 199, 379, 397, 487, 577, 599, 797, 887, 977, 1499, 1697, 1787, 1877, 1949, 2399, 2579, 2687, 2777, 2939, 2957, 2999, 3989, 4799, 4889, 4999, 6997, 7699, 7789, 7879, 8599, 8689, 8779, 8887, 9679, 9697, 9769, 9787, 9859 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The slowest increasing sequence that is a subsequence of A046704 such that the sequence of A007953(a(n)) is nondecreasing. - R. J. Mathar, Mar 29 2010

LINKS

Table of n, a(n) for n=1..48.

EXAMPLE

The first several terms after a(1)=2 are

    3 (3 > 2);

    5 (5 > 3);

    7 (7 > 5);

   29 (2 + 9 > 7);

   47 (4 + 7 = 2 + 9);

   67 (6 + 7 > 4 + 9);

   89 (8 + 9 > 6 + 7);

  179 (1 + 7 + 9 = 8 + 9);

  197 (1 + 9 + 7 = 8 + 9).

MAPLE

A007953 := proc(n) local d ; add(d, d= convert(n, base, 10)) ; end proc:

isA046704 := proc(n) isprime(n) and isprime(A007953(n)) ; end proc:

A156604 := proc(n) option remember ; local psprev, i ; if n = 1 then 2 ; else psprev := A007953(procname(n-1)) ; for i from procname(n-1)+1 do if isA046704(i) then if A007953(i) >= psprev then return i ; end if; end if; end do: end if ; end proc:

seq(A156604(n), n=1..80) ; # R. J. Mathar, Mar 18 2010

From R. J. Mathar, Mar 29 2010: (Start)

A007953 := proc(n) add(d, d= convert(n, base, 10)) ; end proc:

isA028834 := proc(n) local d; add(d, d= convert(n, base, 10)) ; isprime(%) ; end proc:

isA046704 := proc(n) isprime(n) and isA028834(n) ; end proc:

A156604 := proc(n) option remember; if n = 1 then 2; else for a from procname(n-1)+1 do if isA046704(a) and A007953(a) >= A007953(procname(n-1)) then return a; end if; end do: end if; end proc: seq(A156604(n), n=1..100) ; (End)

CROSSREFS

Cf. A000040, A007953, A067954.

Sequence in context: A117299 A091924 A069108 * A046864 A090712 A082257

Adjacent sequences:  A156601 A156602 A156603 * A156605 A156606 A156607

KEYWORD

nonn,base

AUTHOR

Juri-Stepan Gerasimov, Feb 11 2009

EXTENSIONS

Definition, terms and examples corrected by R. J. Mathar, Mar 18 2010

179 and 1877 inserted, and 9 terms after 4889 replaced with the single term 4999, by R. J. Mathar, Mar 29 2010

STATUS

approved

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Last modified October 23 23:51 EDT 2019. Contains 328379 sequences. (Running on oeis4.)