150815

Ruby


隣り合う素数の差と積

オンライン整数列大辞典の
A001223（http://oeis.org/A001223/list）、
A006094（http://oeis.org/A006094/list）
と比較し、答え合わせしてみる。

require 'prime'

def A001223(n)

  ary = Prime.each(n).each_cons(2).map{|c| c[1] - c[0]}

end

ary = A001223(521)

# OEIS A001223のデータ

ary0 =

[1,2,2,4,2,4,2,4,6,2,6,4,2,4,6,6,2,6,4,2,6,4,6,8,

 4,2,4,2,4,14,4,6,2,10,2,6,6,4,6,6,2,10,2,4,2,12,

 12,4,2,4,6,2,10,6,6,6,2,6,4,2,10,14,4,2,4,14,6,10,

 2,4,6,8,6,6,4,6,8,4,8,10,2,10,2,6,4,6,8,4,2,4,12,

 8,4,8,4,6,12]

# 一致の確認

p ary == ary0

def A006094(n)

  ary = Prime.each(n).each_cons(2).map{|c| c[0] * c[1]}

end

ary = A006094(181)

# OEIS A006094のデータ

ary0 =

[6,15,35,77,143,221,323,437,667,899,1147,1517,

 1763,2021,2491,3127,3599,4087,4757,5183,5767,6557,

 7387,8633,9797,10403,11021,11663,12317,14351,

 16637,17947,19043,20711,22499,23707,25591,27221,

 28891,30967,32399]

# 一致の確認

p ary == ary0