A257762 - OEIS

A257762

Numbers n with property that A062234(n) = A062234(n+1).

1, 3, 5, 7, 13, 26, 28, 43, 49, 64, 69, 78, 89, 93, 96, 116, 131, 134, 142, 148, 152, 155, 167, 182, 202, 206, 212, 225, 231, 234, 236, 238, 247, 253, 258, 281, 286, 302, 303, 311, 313, 330, 332, 333, 334, 336, 337, 356, 362, 384, 385, 390, 435, 438, 455, 458, 484, 492, 512, 516

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Numbers n with property that 2*prime(n)-prime(n+1) = 2*prime(n+1)-prime(n+2), or 2*prime(n)+prime(n+2) = 3*prime(n+1).

Numbers n with property that 2*A001223(n) = A001223(n+1). - Gionata Neri, May 22 2015

a(n) = A258432(m), where m such that A258383(m) = 2. - Reinhard Zumkeller, May 31 2015

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1) = A258437(A258432(2)) = 1.

MAPLE

Primes:= select(isprime, [2, (2*i+1 $ i=1..10^4)]):

Gaps:= Primes[2..-1] - Primes[1..-2]:

G2:= Gaps[2..-1] - 2*Gaps[1..-2]:

ListTools:-SearchAll(0, G2); # Robert Israel, May 22 2015

MATHEMATICA

Select[Range@ 600, 2 Prime[#] - Prime[# + 1] == 2 Prime[# + 1] - Prime[# + 2] &] (* Michael De Vlieger, May 11 2015 *)

PROG

(Magma) [n: n in [0..600] | 2*NthPrime(n)-NthPrime(n+1) eq 2*NthPrime(n+1)-NthPrime(n+2)]; // Vincenzo Librandi, May 12 2015

(Haskell)

a257762 n = a257762_list !! (n-1)

a257762_list = map a258432 $ filter ((== 2) . a258383) [1..]

-- Reinhard Zumkeller, May 31 2015

CROSSREFS

Cf. A258383, A258432, A258437, A258469, A257762, A258449, A257892, A257951.

Sequence in context: A154321 A024724 A024946 * A374761 A224222 A224221

Adjacent sequences: A257759 A257760 A257761 * A257763 A257764 A257765

KEYWORD

nonn

AUTHOR

Zak Seidov, May 07 2015

STATUS

approved