A133782 Indices of monotonically increasing primes which centrally enclose the prime sequence in A133781.

31, 32, 36, 40, 187, 321, 327, 452, 580, 590, 821, 831, 940, 942, 946, 955, 965, 1186, 1194, 1198, 1200, 1208, 1213, 419, 429, 2362, 2367, 3348, 3350, 3353, 3372, 3375, 3381, 3383, 4339, 4341, 4347, 5284, 5288, 7995, 8000, 8001, 8009, 8011, 8016, 8887

Offset

1,1

Comments

A break occurs at index 1213 of 9833 and 89 must be centrally located at index 419 prime 2897 and the monotonic sequence resumed from that point onward until the next break occurs

Links

Table of n, a(n) for n=1..46.

Formula

Centrally enclose the prime sequence in another montotonically increasing prime sequence (if a break occurs begin over at that point)

Example

a(23) is the index 1213 of prime 9833 where the prime 83 is centrally located.

Prog

(UBASIC) 10 C=26:Q=str(C):T=443 20 'monotonically increasing primes 30 'centered in primes 40 'change val(m) in 100 50 'adjust T in line 10 after every break 60 N=101 70 A=3:S=sqrt(N) 80 B=N\A 90 if B*A=N then N=N+2:goto 70 100 A=A+2 110 if A<=sqrt(N) then 80 120 Z=str(N):W=alen(N):W=W-2:M=mid(Z, 3, W): if M=Q then print C, N:stop 130 if val(M)=nxtprm(T) then print Q, M, Z:T=val(M):stop 140 C=C+1:Q=str(C) 150 N=N+2:goto 70

Crossrefs

Cf. A133781 A075595.

Sequence in context: A165852 A291523 A256496 * A022401 A042936 A042934

Adjacent sequences: A133779 A133780 A133781 * A133783 A133784 A133785

Keyword

easy,nonn,uned

Author

Enoch Haga, Sep 23 2007

Status

approved