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 A320882 Primes p such that repeated application of A062028 (add sum of digits) yields two other primes in a row: p, A062028(p) and A062028(A062028(p)) are all prime. 1
 11, 59, 101, 149, 167, 257, 277, 293, 367, 419, 479, 547, 617, 727, 839, 1409, 1559, 1579, 1847, 2039, 2129, 2617, 2657, 2837, 3449, 3517, 3539, 3607, 3719, 4217, 4637, 4877, 5689, 5779, 5807, 5861, 6037, 6257, 6761, 7027, 7489, 7517, 8039, 8741, 8969, 9371, 9377, 10667, 10847, 10937, 11257, 11279, 11299, 11657 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS "Iterates" the idea of A048519 (p and A062028(p) are prime), also considered in A048523, A048524, A048525, A048526, A048527. (This is the union of A048524, A048525, A048526, A048527 etc. A048525(1) = 277 = a(7).) LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE f:= n -> n + convert(convert(n, base, 10), `+`): filter:= proc(n) local x; if not isprime(n) then return false fi; x:= f(n); isprime(x) and isprime(f(x)) end proc: select(filter, [seq(i, i=3..10000, 2)]); # Robert Israel, Dec 17 2020 PROG (PARI) is_A320882(n, p=n)=isprime(p=A062028(p))&&isprime(A062028(p))&&isprime(n) \\ Putting isprime(n) to the end is more efficient for the frequent case when the terms are already known to be prime. forprime(p=1, 14999, isprime(q=A062028(p))&&isprime(A062028(q))&&print1(p", ")) CROSSREFS Subsequence of A048519: p and A062028(p) are prime. Cf. A047791, A048520, A006378, A107740, A243441 (p and p + Hammingweight(p) are prime), A243442 (analog for p - Hammingweight(p)). Cf. A048523, ..., A048527, A320878, A320879, A320880: primes starting a chain of length 2, ..., 9 under iterations of A062028(n) = n + digit sum of n. Sequence in context: A214151 A273618 A168539 * A048524 A186312 A142401 Adjacent sequences:  A320879 A320880 A320881 * A320883 A320884 A320885 KEYWORD nonn,base AUTHOR M. F. Hasler, Nov 06 2018 STATUS approved

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Last modified May 16 11:05 EDT 2021. Contains 343941 sequences. (Running on oeis4.)