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A260523 Numbers n such that (sum of digits of n) + (product of digits of n) is semiprime. 1
2, 3, 5, 7, 14, 17, 24, 28, 33, 38, 39, 40, 41, 42, 46, 47, 49, 55, 60, 64, 67, 68, 69, 71, 74, 76, 82, 83, 86, 90, 93, 94, 96, 103, 105, 108, 109, 111, 112, 114, 116, 121, 122, 124, 126, 130, 141, 142, 144, 146, 150, 161, 162, 164, 166, 180, 190, 202, 204, 207 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..10000

EXAMPLE

a(6) = 17. (1+7) + (1*7) = 8 + 7 = 15 = 3 * 5, which is semiprime.

a(10) = 38. (3+8) + (3*8) = 11 + 24 = 35 = 5 * 7, which is semiprime.

MAPLE

with(numtheory):A260523 := proc() local a; a:= (add(d, d=convert(n, base, 10)) + mul(d, d=convert(n, base, 10))  ); if bigomega(a)=2 then RETURN (n); fi; end: seq(A260523 (), n=1..300);

MATHEMATICA

Select[Range[1000], PrimeOmega[(Plus@@IntegerDigits[#]) + (Times@@IntegerDigits[#])] == 2 &]

PROG

(PARI) for(n=1, 500, d=digits(n); s=sumdigits(n); p=prod(i=1, #d, d[i]); if(bigomega(s+p)==2, print1(n, ", "))) \\ Derek Orr, Aug 27 2015

CROSSREFS

Cf. A001358, A007953, A007954, A061762, A214629.

Sequence in context: A031345 A206702 A279953 * A114625 A046808 A097799

Adjacent sequences:  A260520 A260521 A260522 * A260524 A260525 A260526

KEYWORD

nonn,base,easy

AUTHOR

K. D. Bajpai, Jul 28 2015

STATUS

approved

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Last modified October 24 20:35 EDT 2021. Contains 348233 sequences. (Running on oeis4.)