A077138
a(0) = 0. If n is odd, a(n) = a(n-1) + n, otherwise a(n) = a(n-1) * n.
Original entry on oeis.org
0, 1, 2, 5, 20, 25, 150, 157, 1256, 1265, 12650, 12661, 151932, 151945, 2127230, 2127245, 34035920, 34035937, 612646866, 612646885, 12252937700, 12252937721, 269564629862, 269564629885, 6469551117240, 6469551117265, 168208329048890
Offset: 0
- William Boyles, Table of n, a(n) for n = 0..1000 [Terms 0 through 26 were computed by Amarnath Murthy; terms 27 through 1000 were computed by William Boyles, Nov 27 2016]
-
a = 0; Table[If[OddQ[n], a = n + a, a = n*a], {n, 0, 30}] (* T. D. Noe, Feb 26 2013 *)
nxt[{n_,a_}]:={n+1,If[EvenQ[n],a+n+1,a(n+1)]}; NestList[nxt,{0,0},30][[All,2]] (* Harvey P. Dale, Feb 13 2022 *)
-
a(n)=if(n<0,0,if(n%2,n+a(n-1),n*a(n-1)))
-
a=0
for n in range(1, 33):
print(a, end=', ')
if n&1:
a += n
else:
a *= n
A332657
Alternate adding and multiplying prime numbers: a(2n) = a(2n-1) * prime(2n+1) and a(2n-1) = a(2n) + prime(2n-2) for n >= 1.
Original entry on oeis.org
5, 25, 32, 352, 365, 6205, 6224, 143152, 143181, 4438611, 4438648, 181984568, 181984611, 8553276717, 8553276770, 504643329430, 504643329491, 33811103075897, 33811103075968, 2468210524545664, 2468210524545743, 204861473537296669, 204861473537296758
Offset: 1
a(1) = 2 + 3 = 5;
a(2) = 5 * 5 = 25;
a(3) = 25 + 7 = 32;
...
a(40) = 2714410084880275101596278688487175846.
-
from sympy import primerange
p = list(primerange(1, 200))
def a(n):
out = p[0] + p[1]
for i in range(1, n):
if i % 2:
out *= p[i + 1]
else:
out += p[i + 1]
return out
for n in range(1, 25):
print(a(n), end=", ")
A332659
Alternate multiplying and adding prime numbers: a(2n) = a(2n-1) + prime(2n+1) and a(2n-1) = a(2n) * prime(2n-2) for n >= 1.
Original entry on oeis.org
6, 11, 77, 88, 1144, 1161, 22059, 22082, 640378, 640409, 23695133, 23695174, 1018892482, 1018892529, 54001304037, 54001304096, 3294079549856, 3294079549923, 233879648044533, 233879648044606, 18476492195523874, 18476492195523957, 1644407805401632173
Offset: 1
a(1) = 2 * 3 = 6;
a(2) = 6 + 5 = 11;
a(3) = 11 * 7 = 77.
A332660
Alternate adding and multiplying Fibonacci numbers: a(0) = F(0) + F(1), for n >= 0, a(2n+1) = a(2n) * F(2n+2), a(2n+2) = a(2n+1) + F(2n+3).
Original entry on oeis.org
1, 1, 3, 9, 14, 112, 125, 2625, 2659, 146245, 146334, 21072096, 21072329, 7944268033, 7944268643, 7840993150641, 7840993152238, 20261126305382992, 20261126305387173, 137066519455944225345
Offset: 0
a(0) = 0 + 1 = 1;
a(1) = 1 * 1 = 1;
a(2) = 1 + 2 = 3;
a(3) = 3 * 3 = 9;
a(4) = 9 + 5 = 14.
-
a[0] = 1; a[n_] := a[n] = If[OddQ[n], a[n-1] * Fibonacci[n+1], a[n-1] + Fibonacci[n+1]]; Array[a, 20, 0] (* Amiram Eldar, Mar 28 2020 *)
-
from sympy import fibonacci
f = [fibonacci(n) for n in range(100)]
def a(n):
out = f[0] + f[1]
for i in range(1, n):
if i%2:
out *= f[i+1]
else:
out += f[i+1]
return out
A333591
Alternate multiplying and adding Fibonacci numbers: a(0) = F(0) * F(1), for n >= 0, a(2n+1) = a(2n) + F(2n+2), a(2n+2) = a(2n+1) * F(2n+3).
Original entry on oeis.org
0, 1, 2, 5, 25, 33, 429, 450, 15300, 15355, 1366595, 1366739, 318450187, 318450564, 194254844040, 194254845027, 310224987508119, 310224987510703, 1297050672782249243, 1297050672782256008, 14197516664274574263568, 14197516664274574281279
Offset: 0
a(0) = 0 * 1 = 0;
a(1) = 0 + 1 = 1;
a(2) = 1 * 2 = 2;
a(3) = 2 + 3 = 5;
a(4) = 5 * 5 = 25.
-
a[0] = 0; a[n_] := a[n] = If[EvenQ[n], a[n-1] * Fibonacci[n+1], a[n-1] + Fibonacci[n+1]]; Array[a, 22, 0] (* Amiram Eldar, Mar 28 2020 *)
-
from sympy import fibonacci
f = [fibonacci(n) for n in range(200)]
def a(n):
out = f[0] * f[1]
for i in range(1, n+1):
if i%2:
out += f[i+1]
else:
out *= f[i+1]
return out
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