A124436 a(1)=1, a(n)=p_i^d_i where p_i is i-th prime and d_i is i-th digit of a(n-1).

1, 2, 4, 16, 1458, 2918430506250, 7164640537512654203797788776525821310188011060

Offset

1,2

Comments

Or a(n-1)= decimal encoding of the prime factorization of a(n). Cf. A068633 Let n = p^a*q^b... then a(n) = concatenation paqb..., A067599 Decimal encoding of the prime factorization of n.

The next term (a(8)) has 330 digits and a(9) has 3882 digits. - Harvey P. Dale, Oct 24 2025

Links

Table of n, a(n) for n=1..7.

Example

a(4)=16, a(5)=2^1 * 3^6 = 1458;
a(6)= 2^1 * 3^4 * 5^5 * 7^8 = 2918430506250.

Mathematica

a[1]=1; id[n_]:=id[n]=IntegerDigits[a[n-1]]; a[n_]:=a[n]= Times@@Table[Prime[i]^id[n][[i]], {i, 1, Length[id[n]]}]; {1, Table[a[n], {n, 2, 7}]}//Flatten
NestList[Times@@(Prime[Range[IntegerLength[#]]]^IntegerDigits[#])&, 1, 6] (* Harvey P. Dale, Oct 24 2025 *)

Crossrefs

Cf. A067599, A068633.

Sequence in context: A371717 A001128 A280890 * A369378 A014221 A249760

Adjacent sequences: A124433 A124434 A124435 * A124437 A124438 A124439

Keyword

base,nonn

Author

Zak Seidov, Dec 16 2006

Status

approved