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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.
9
2, 11, 11, 277, 37783, 516493, 286330897, 286330897, 56676324799
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
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.
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).
Sequence in context: A292779 A245521 A275617 * A153706 A201187 A359207
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