A075523 -id:A075523

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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.

+20
2

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

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

OFFSET

1,4

COMMENTS

a(A075521(n)) > 1;

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

LINKS

Table of n, a(n) for n=1..105.

EXAMPLE

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.

CROSSREFS

Cf. A075520, A075519.

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Sep 19 2002

STATUS

approved

A075524

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

+10
2

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

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

OFFSET

1,1

LINKS

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

MATHEMATICA

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

PROG

(Haskell)

a075524 n = a075524_list !! (n-1)

a075524_list = filter ((== 0) . a010051') a075520_list

-- Reinhard Zumkeller, Feb 20 2012