A075523 -id:A075523 - cp's OEIS frontend

A075522 Number of steps to reach the first nonprime (=A075523(n)) starting with the n-th prime p and iterating the map k -> 4*k+(p mod 4), or -1 if no integer is ever reached.

1, 1, 1, 3, 3, 2, 1, 2, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 3, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 4, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 3, 1, 1, 1, 1, 1, 3, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4

Offset: 1

Reinhard Zumkeller, Sep 19 2002

nonn

a(A075521(n)) > 1;

a(n) = a(A075520(n))+1 for n with A075520(n) prime.

			A000040(4)=7 and (7 mod 4) = 3: 7 -> 4*7+3=31 -> 4*31+3=127 -> 4*127+3=511 = A075523(4), therefore a(4)=3.

Cf. A075520, A075519.

A075524 Nonprimes of form 4*p + (p mod 4), p prime.

Original entry on oeis.org

10, 15, 21, 69, 95, 117, 165, 175, 213, 245, 287, 319, 335, 357, 405, 415, 437, 453, 511, 527, 549, 559, 597, 629, 655, 671, 693, 725, 767, 789, 799, 847, 895, 917, 933, 959, 965, 1007, 1029, 1055, 1077, 1125, 1135, 1173, 1247, 1253, 1269, 1349, 1391

Offset: 1

Reinhard Zumkeller, Sep 19 2002

nonn

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Cf. A075520, A075523.

a075524 n = a075524_list !! (n-1)
a075524_list = filter ((== 0) . a010051') a075520_list
-- Reinhard Zumkeller, Feb 20 2012

Select[4#+Mod[#,4]&/@Prime[Range[100]],!PrimeQ[#]&] (* Harvey P. Dale, Nov 21 2012 *)

cp's OEIS Frontend

A075522 Number of steps to reach the first nonprime (=A075523(n)) starting with the n-th prime p and iterating the map k -> 4*k+(p mod 4), or -1 if no integer is ever reached.

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A075524 Nonprimes of form 4*p + (p mod 4), p prime.

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