A059417 Start with 1; square; add 2; subtract 1; repeat.

1, 1, 3, 2, 4, 6, 5, 25, 27, 26, 676, 678, 677, 458329, 458331, 458330, 210066388900, 210066388902, 210066388901, 44127887745906175987801, 44127887745906175987803, 44127887745906175987802

Offset: 0

Author

Jonathan Scharff (jonscharff(AT)home.com), Jan 30 2001

Keywords

• easy
• nonn

Comments

a(22) has 46 digits.

References

• Seen on a quiz.

Links

• Harry J. Smith, Table of n, a(n) for n = 0..36

Crossrefs

Cf. A004019.

Programs

Mathematica

Flatten@ NestList[# + {0, 2, 1} &[Last[#]^2] &, {1}, 7] (* Michael De Vlieger, Sep 06 2016 *)

PARI

{ for (n = 0, 36, if (n==0, a=1, if (n%3 == 1, a*=a, if (n%3==2, a+=2, if (n%3==0, a-=1)))); write("b059417.txt", n, " ", a); ) } \\ Harry J. Smith, Jun 26 2009

Formula

a(1+3k) = A004019(k+1), a(2+3k) = A004019(k+1)+2, a(3+3k) = A004019(k+1)+1, k>=0. - Yuriy Sibirmovsky, Sep 04 2016

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Jan 31 2001