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A270142 a(n) = product of first k composites, with the i-th composite raised to the d-th power, where k = A055642(n) and d is the i-th digit of n. 1
4, 16, 64, 256, 1024, 4096, 16384, 65536, 262144, 4, 24, 144, 864, 5184, 31104, 186624, 1119744, 6718464, 40310784, 16, 96, 576, 3456, 20736, 124416, 746496, 4478976, 26873856, 161243136, 64, 384, 2304, 13824, 82944, 497664, 2985984, 17915904, 107495424 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are multiples of 4, since A002808(1) = 4 and the most significant digit of n is always nonzero.

Does a term exist such that a(n) = n? Such a number would be the analog of a Meertens number when raising composites to the powers of the digits of n instead of raising primes to the powers of the digits.

LINKS

Felix Fröhlich, Table of n, a(n) for n = 1..10000

EXAMPLE

a(12) = 144, since A002808(1) = 4, A002808(2) = 6 and 4^1 * 6^2 = 144.

PROG

(PARI) composite(n) = my(i=0, c=2); while(1, if(!ispseudoprime(c), i++); if(i==n, return(c)); c++)

compopowerprod(n) = my(d=digits(n)); for(k=1, #d, p=prod(i=1, #d, composite(i)^d[i])); p

a(n) = compopowerprod(n)

CROSSREFS

Cf. A189398, A246532.

Sequence in context: A215877 A206450 A294452 * A000302 A262710 A050734

Adjacent sequences:  A270139 A270140 A270141 * A270143 A270144 A270145

KEYWORD

nonn,base,easy

AUTHOR

Felix Fröhlich, Mar 12 2016

STATUS

approved

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Last modified February 21 02:19 EST 2018. Contains 299388 sequences. (Running on oeis4.)